WI Hitler conquers Britain?

[Michele]

there is the problem that the majority of Americans really didn't want to go to war in Europe, even though most of them thought little of Hitler and his goons. It took Pearl Harbor and Hitler declaring war on us to drag us into it. There's nothing in this POD that seems like it would butterfly away Japan's coming war with the USA (the same problems exist), but the onus of declaring war is still on Hitler...

Sorry, but that was true until 1939-early 1940.
While we don't really know a lot about what people thought in dictatorships like Germany, Italy, Japan and the USSR, we do have a wealth of Gallup and other polls concerning what people thought in the USA. Many can be looked up online. Do so. You will see that people were changing their minds. The fall of France was a rude wake-up. Then, for a few months, the idea was to stay out of the war but to supply, in a clearly non-neutral way, those who were fighting it, and to risk actual war in order to do so. Meanwhile, the other factor apart from the public opinion was the decision maker, i.e. FDR; he had already decided for that sort of commitment in resources, and was pushing for an active participation in the war.
In OTL, had Hitler not declared war on the USA, the reverse would have happened, within maybe 6 months.

In this scenario, the fall of Britain is an alarm ten times stronger than the fall of France. As to the casus belli, abundant reasons will remain, because the USA will keep supporting the BCE which will be fighting the German-Italian troops at the edges of the theater, and sending supplies to the Soviet Union (i.e the U-Boote will continue sinking US merchant ships and USN warships just as in OTL before the declaration of war).

---

Edited to provide a few data pointers.

As of June 1940, when France had not fallen yet, the majority of polled US citizens thought that the USA should stay out of the war, rather than help "England" at the risk of being dragged in the war.
The turning point was in September 1940, at the time of the Battle of Britain; more than 50% of the US citizens then thought that helping "England" was worth the risk of being sucked into the war. That opinion hovered above 60% for most of 1941, and reached 70% in October 1941.

A part of those in favor of helping "England" even at the risk of war, actually just wanted outright war already against Germany and Italy. That part was 12% of the polled people in January 1940, and was 24% in June 1941.

In April 1941, the interesting question was asked whether the respondent thought that the USA would enter the European war before it would be over. 82% of the polled US citizens thought so.

Particularly relevant to the thread, i.e. to the issue of the fall of Britain. In May 1941, the question was asked: "Would you rather see Britain surrender to Germany than have the United States go into the war?" The answer was:
No 62%
Yes 26%
No opinion 12%

 

[Meadow]

Then the problem is more serious.



Think before writing. The USA did get involved in a war against Japan, even though they had no bases to attack Japan from.

The reason why the USA would go to war against Germany is that it is not in the interest of the USA to have a hegemonic power in control of Europe, Africa, and some important bit of Asia. Especially if it's a hostile power, but frankly, in any case. That's why. And they would procure the land and build the infrastructure to have bases to attack from - just like they did in the Japanese case.

Your tone is rude and indicates you are not interested in actual discussion, but rather bullying others into agreeing with you. As someone who has behaved in this way in the past, I can recommend that you chill out a bit and stop it - it doesn't lead anywhere pleasant.

For now, though, I'm not going to engage with this.

 

[Michele]

Your tone is rude and indicates you are not interested in actual discussion, but rather bullying others into agreeing with you. As someone who has behaved in this way in the past, I can recommend that you chill out a bit and stop it - it doesn't lead anywhere pleasant.

For now, though, I'm not going to engage with this.

You are right that my tone is rude and I apologise for that. On the other hand, it only indicates that I have little patience for posters who write without thinking and make claims without knowing. You can read my previous post, for starters, as to the real outlook.

 

[zoomar]

I can see Ireland entering the war on the side of the Allies and an eventual liberation of Britain by the Americans launched from there. If not, the Americans could simply launch an invasion of Europe through the Mediterranean via southern France and Italy.

Actually, If Britain is conquered by the Nazis, why wouldn't they just go on and occupy (a weak and largely defenseless) Ireland to eliminate this possibility.

Also, if the USA is not already at war with Germany, it seems very unlikely that the US would go to war with Germany after the conquest of Britain - unless Germany provokes the US. The logistics of waging a true transatlantic war are daunting (actually impossible in 1940-1944). Since the main possible provocations in 1939-1940 involved the U-boat war, this will not be an issue if Britain falls. The US will not be shipping anything to Britain...and if it wishes to continue a lend-lease arrangement with the USSR, shipping and flights can go thru Alaska and Siberia, with minimal risk from German submarines. Frankly, if Britain falls, there is no longer anything such as "the Allies". There is just the USSR, and like others, I just don't see the US being all that excited about assisting Stalin...unless it is really just to keep the USSR going just long enough to bleed and weaken both totalitarian states.

The only way the US might stay engaged enough to eventually enter the war is if a substantial British government in exile is established in Canada that clearly has broad support throughout the British Empire, and which continues the war against Germany. I also don't see why the Royal Family would not decamp to Canada along with the Royal Navy and the exile government. The King is as much the head of state of Canada as he is of Great Britain. Canada is still technically part of an "empire" after all so there seems to me to be no reason the Government of the entire British Empire can't move to Ottawa. Germany is fighting the British Empire, not just England. Should Germany find it necessary to attack(air or ground) British territory in or Near North America, that would be an immediate threat the US that might prompt US entry in the war.

 

[zoomar]

Think before writing. The USA did get involved in a war against Japan, even though they had no bases to attack Japan from.

Uh...first,the US was directly attacked by Japan. Second, several US possessions in the western Pacific were invaded and occupied by Japan. Third, US war planners presumed that any war against Japan could be successfully won by sea power (and later airpower) alone, so Japan itself did not need to be invaded. Any plan to defeat Nazi Europe prior to the development of true transcontinental airpower and nuclear weapons (1947-48) would require a massive US invasion and the most obvious staging points were either neutral or enemy territory. Geopolitically and diplomatically, the situation in the Atlantic and Pacific was not remotely the same.

 

[Michele]

Uh...first,the US was directly attacked by Japan. Second, several US possessions in the western Pacific were invaded and occupied by Japan. Third, US war planners presumed that any war against Japan could be successfully won by sea power (and later airpower) alone, so Japan itself did not need to be invaded. Any plan to defeat Nazi Europe prior to the development of true transcontinental airpower and nuclear weapons (1947-48) would require a massive US invasion and the most obvious staging points were either neutral or enemy territory. Geopolitically and diplomatically, the situation in the Atlantic and Pacific was not remotely the same.

First, all of the above are not the same objection as the one I was replying to.

Second, the USA were also directly attacked by Germany. In OTL. Before December 1941.

Third, I'd like to see those assessments concerning sea and air power to defeat Japan by US planners. Apparently, the, well, US planners who wrote the plans for Olympic and Coronet had not heard about those assessments.

Fourth, yes, the most obvious staging points for entry into continental Europe were in neutral hands - you know, like Vichy France, operation Torch.

Fifth, talking about Torch - there you have it, your transatlantic projection of force. TF 34 counted some 100 ships, and the operation was successful. Could that force do an Overlord? No. That's why a peripheral area, with murky politics, hard to reinforce for the enemy, was chosen, and why such an area would be chosen in this scenario.

Sixth, yes, the two theaters were different - but not for the reasons you list, which, as you can see, are faulty.

 

[Michele]

Also, if the USA is not already at war with Germany, it seems very unlikely that the US would go to war with Germany after the conquest of Britain -

Save for the rock-solid foundation of the obvious reason for which most wars are waged for - national interest.

And there is this, too:

In May 1941, the question was asked: "Would you rather see Britain surrender to Germany than have the United States go into the war?" The answer was:
No 62%
Yes 26%
No opinion 12%

 

[zoomar]

First, all of the above are not the same objection as the one I was replying to.

Second, the USA were also directly attacked by Germany. In OTL. Before December 1941.

Third, I'd like to see those assessments concerning sea and air power to defeat Japan by US planners. Apparently, the, well, US planners who wrote the plans for Olympic and Coronet had not heard about those assessments.

Fourth, yes, the most obvious staging points for entry into continental Europe were in neutral hands - you know, like Vichy France, operation Torch.

Fifth, talking about Torch - there you have it, your transatlantic projection of force. TF 34 counted some 100 ships, and the operation was successful. Could that force do an Overlord? No. That's why a peripheral area, with murky politics, hard to reinforce for the enemy, was chosen, and why such an area would be chosen in this scenario.

Sixth, yes, the two theaters were different - but not for the reasons you list, which, as you can see, are faulty.

First, the US was NOT directly attacked by Nazi Germany prior to Dec 7, 1941. Neither I nor apparently the US government considered the sinking of a few merchants and even US destroyers in FDR's undeclared anti-submarine campaign a direct attack on the US or we would have declared war on Germany then. If Britain had fallen most of potential for this providing a serious German provocation is gone. It is also worth noting that even after December 7, the US only declared war on Japan.

Second. I strongly suggest that you study War Plan Orange. An excellent source is Edward Miller's War Plan Orange: The US Strategy to Defeat Japan 1897-1945, USNI Press. Throughout this entire period, the US always planned on defeating Japan through a strategy of beating the Japanese navy, naval blockade, and from about 1930 on, a sustained strategic bombing campaign. The idea of invading Japan proper was never considered. Coronet and Olympic were both fallback options and it is by no means certain they would have been mounted even absent the atomic bombs.

With regard to Torch, you are presuming several things that might not apply in a Britain Falls in 1940 scenario. In this TL, there would be probably not be any British presence remaining in North Africa. But that is quibbling. First you have to have a situation in which the US and Germany are at war to make the US consider mounting an invasion in the first place. Since actual combat between USN and KM warships in the North Atlantic was not sufficient to prompt a US declaration of war with Britain still in the fight, what do you propose as a provocation after Britain falls when the US is no longer protecting Britain-bound convoys? Provide a plausible provocation and I can provide a plausible plan for the US to begin invading Europe.

I don't deny that the US will most likely eventually end up at war with Nazi Germany, but it will not happen immediately upon the collapse of Britain, but be provoked by some future events that we can only speculate upon. It might happen in 1942, 1944, 1946 or 1949. Who knows?

Finally, I would not place so much emphasis on polling data. Public opinion survey were in their infancy in the 1940's and, as you well know, public opinion does not always dictate what a government will actually do.

 

[MonaroLS]

The islands may be under the Jackboot, but what about the Commonwealth. Canada, SA, India, Oz and NZ are still alive and kicking. There will undoubtedly be a British Govt in exile (probably in Canada). There will be British troops in Egypt which won't surrender.
Would the US supply material to the remainding elements of the Empire. I think so, starting with The army in Egypt. It would be a race to get the stuff there before the Germans get their act together in North Africa.
In my opinion that is where the action will come from.
Oh, and Japan wouldn't get any resources from any parts of Malaysia or DEI without have to attack as per OTL. And then it will really hit the fan.

 

[Michele]

First, the US was NOT directly attacked by Nazi Germany prior to Dec 7, 1941. Neither I nor apparently the US government considered the sinking of a few merchants and even US destroyers in FDR's undeclared anti-submarine campaign a direct attack on the US or we would have declared war on Germany then.

So it is you who decide that the sinking of a warship is not a direct attack?

As to the fact that war was not declared for that, sure. I could list a long, long list of cases in which direct hostile acts did not bring about a declaration of war by the victim. That does not make them less hostile.

If Britain had fallen most of potential for this providing a serious German provocation is gone.

Yes, your mistake here is to go with the basic flawed assumption of this thread, i.e., let's ignore how that happens, i.e., let's basically assume it happens overnight.
In reality, even an ASB-supported German success in Britain would take months of active war. Months during which the USA would have done their best to supply the british forces fighting there (remember the question about letting Britain surrender?). IOW, months during which US ships would have been sunk by U-Boote.

It is also worth noting that even after December 7, the US only declared war on Japan.

Sure. And the overwhelming majority of US citizens thought, by then, that a declaration of war against Germany should have taken place. Also, asked on 15.11.1941:
Which of these two things do you think is the more important — that this country keep out of war, or that Germany be defeated?

Keep out of war 32%

Defeat Germany 68%

I cut out parts that are made irrelevant by the above. By the way, the reason why I mentioned Torch isn't to say that exactly the same thing would happen. The reason is that you and others here keep making statements and comparisons that run directly contrary to actual history.

1. The USA wouldn't declare war on a country they have no bases to attack from - the USA actually declared war on Japan and then went on to conquer the bases and develop the infrastructures, say Tinian (this wasn't yours, but the following are).
2. The USA was directly attacked by Japan but not by Germany - Germany damaged and sank several US warships prior to the declaraiton of war.
3. Cross-Atlantic invasions were impossible until say 1945 - Torch took place in 1942.
4. Suitable landing places would be neutral and that would be a problem - landing in neutral Vichy French territory was not a problem.

You'll pardon me if I find that a position that is built upon such a terrible ignorance of actual history can only be terribly wrong.

Finally, I would not place so much emphasis on polling data. Public opinion survey were in their infancy in the 1940's and, as you well know, public opinion does not always dictate what a government will actually do.

You are right there. In fact, the US administration at the time was seeing farther out than its own public opinion. The President wanted war against the Axis far more than his own voters. Nowadays, we see the Lend-Lease idea as part of the furniture, but at the time it was a major, major departure from accepted policy by a neutral. The ABC-1 Staff Agreements are dated march 1941, and had come into being after three months of talks.
The government, in practice, was already aware that war against the European Axis was necessary; they just needed to convince the population of that.
Had Roosevelt been a dictator, yes, the public opinion would not have dictated what his government would have actually done - and that would have been to go to war.

 

[Cronos988]

Why would the US get involved in a war against a nation it no longer has any bases attack from?

Um, aren't you forgetting something rather larger, rather red, and right next to Germany?

I can see an increase in support for the Soviet Union, but that has a ceiling of 'but they're commies'

No it doesn't. During WW 2, the "commies" are the good guys. Don't let post war thinking (i.e. Britain and US are close, SU and US are enemies) color your thinking. During WW2, US policy was arguably more friendly towards the SU (partly because Stalin got on really well with FDR) than it was to Britain, which at the time was viewed by many high-ranking american officials as an uncaring, imperialistic power only out to save it's colonies.

In this ATL, with Britain out of the war, the US and the SU will be very closely allied, and the alliance will start (probably secretly, at first) pretty much as soon as it's obvious that Britain will fall. Both Stalin and FDR know what comes next. Both of them want Hitler gone.

and even if the US wanted to send expeditionary forces to Vladivostok, Stalin isn't going to let them fight alongside the Red Army unless there's a setup of the chain of command that's unacceptable to the US.

OTL, yes, ITTL, not necessarily. If it's necessary, Stalin will allow the US an independent command. They did it for an american bombing force, but unfortunately that force was destroyed in one devastating german raid.

'we love freedom' isn't going to be enough to make the US sew wings onto the Big Red One and fly them to Berlin, I'm afraid. And besides, you only have to look at how long Saudi Arabia and North Korea have been around to see that a US with the greatest force projection in human history is prepared to leave horrific regimes in place if politics requires it.

But in the case of FDR, politics requires that the Axis is gone, because FDR's main political goal is setting up a new order for world peace, aka the United Nations. That means as long as someone is fighting against Germany, the US under FDR will fight with them.

 

[Michele]

But in the case of FDR, politics requires that the Axis is gone, because FDR's main political goal is setting up a new order for world peace, aka the United Nations. That means as long as someone is fighting against Germany, the US under FDR will fight with them.

Yes, that's not wrong, but it's not the whole story. There's more to the war than that, just like there's more than "we love freedom" and more than "we were bombed at Pearl and declared war upon by Germany".

IMHO, a really comprehensive story of why the USA were in this war has to start in 1853, in the bay of Tokyo.

 

[zoomar]

The reason is that you and others here keep making statements and comparisons that run directly contrary to actual history.

1. The USA wouldn't declare war on a country they have no bases to attack from - the USA actually declared war on Japan and then went on to conquer the bases and develop the infrastructures, say Tinian (this wasn't yours, but the following are).
2. The USA was directly attacked by Japan but not by Germany - Germany damaged and sank several US warships prior to the declaraiton of war.
3. Cross-Atlantic invasions were impossible until say 1945 - Torch took place in 1942.
4. Suitable landing places would be neutral and that would be a problem - landing in neutral Vichy French territory was not a problem.

You'll pardon me if I find that a position that is built upon such a terrible ignorance of actual history can only be terribly wrong.

You are both misrepresenting what I and others have said and/or insist on squeezing it into your preconceived template of what you imagine we are saying...and then you insult us. Your own willful disregard for the facts is clearly indicated in your point #2. The US declared war on Japan because of a direct attack on US territory...no matter how you define things Germany did not do that. The naval engagements I described (and you seem to feel are equivalent to Pearl Harbor) did not lead to a US declaration of war on Germany prior to the hypothetical defeat of Britain so why on earth can you imagine they would after Britain is defeated. Assuming that any further incidents would occur, of course. You fail to grasp that, if Britain is defeated by Germany there will no longer be convoys heading from North America to Britain, and hence far less likelihood that U-boats will be prowling the N Atlantic Sea lanes and US Destroyers looking for them. You are free to speculate, I suppose, that if an Exiled British regime stays in the fight in Canada, it will seek to maintain supplies to other hypothetical Exile British Forces fighting in North Africa, but it is a stretch to automatically presume the US would provide naval escorts for these ships. Basically, you have yet to adequately justify your opinion that the US would declare war on Germany upon the defeat and occupation of the British Isles. And unless the US and Germany are at war, there will be no Torches being planned irrespective of their feasibility in 1942 or later.

 

[Michele]

You are both misrepresenting what I and others have said and/or insist on squeezing it into your preconceived template of what you imagine we are saying...

Not in the least. Look up the posts. I'm just reading what you and others write. For instance:

Your own willful disregard for the facts is clearly indicated in your point #2. The US declared war on Japan because of a direct attack on US territory...no matter how you define things Germany did not do that.

Sure. The only small detail is the clause "on US territory" you had to add now. You had to rephrase your initial claim, which did not specify where a direct attack was made.
Sorry if I reply to what you write and am unable to read in your mind what you meant.

If anyone here is imagining things, it's you. You are imagining that you have already made the distinction about attacks on US territory or not. The reality is you did not.
Go read your own posts.

If you'd like to move the discussion in a more productive direction, you could drop this sort of indefensible posturing and address the issue I raised in reply to Cronos988. Do you really believe the reason why the USA entered the war can be sufficiently described as: the Japanese bombed Pearl Harbor and the Germans and Italians declared war?

 

[zoomar]

Um, aren't you forgetting something rather larger, rather red, and right next to Germany?



No it doesn't. During WW 2, the "commies" are the good guys. Don't let post war thinking (i.e. Britain and US are close, SU and US are enemies) color your thinking. During WW2, US policy was arguably more friendly towards the SU (partly because Stalin got on really well with FDR) than it was to Britain, which at the time was viewed by many high-ranking american officials as an uncaring, imperialistic power only out to save it's colonies.

In this ATL, with Britain out of the war, the US and the SU will be very closely allied, and the alliance will start (probably secretly, at first) pretty much as soon as it's obvious that Britain will fall. Both Stalin and FDR know what comes next. Both of them want Hitler gone.



OTL, yes, ITTL, not necessarily. If it's necessary, Stalin will allow the US an independent command. They did it for an american bombing force, but unfortunately that force was destroyed in one devastating german raid.



But in the case of FDR, politics requires that the Axis is gone, because FDR's main political goal is setting up a new order for world peace, aka the United Nations. That means as long as someone is fighting against Germany, the US under FDR will fight with them.

I disagree with most of what you are saying, especially with respect to the USSR and USA. You are aware that the USA only recognized the Soviet Union in the early 1930's, right? I also trust you are aware that anti-communism was probably as prevalent in the 1940 US Congress and population in general as during the cold war. And surely you appreciate that, in 1940 or early 1941, when this imagined German defeat of Britain would have occurred, the USSR was in effect an ally of Hitler's Germany. The whole myth of "uncle Joe Stalin" and the fact of US/USSR friendship only developed after the US entered WW2 and it became necessary for propagandists to paper over the inconvenient fact that Stalin's Russia was almost as reprehensible as Hitler's Germany. FDR may have had some grand plans, but he had to use every legal and quasi-legal means at his disposal to assist Democratic and Capitalist Britain in 1939-1940/41, and this did not include going to war. Only if the US was already at war with Germany when Hitler invaded the USSR can we presume that the US would adopt a friendly posture toward Stain and the Soviet Union. Since it is reasonable to presume the US would not have declared war on Nazi Germany prior to that date (we didn't OTL after all) then it is highly unlikely FDR could get the US congress to go along with a declaration of war against Germany in alliance with the USSR. Once Japan attacks the US, it's entirely up in the air whether the US would adopt a "Germany First" strategy - or even declare war on Germany if Hitler doesn't do this first. My own thought is that the US would eventually enter the Russo-German War but drive a hard bargain with Stalin...we'll help you if you help us in Asia (ie: declare war on Japan, give us air bases in eastern Russia to use against the Japanese, and invade Manchuria)

 

[zoomar]

Michele,

Here is what I wrote:

First, the US was NOT directly attacked by Nazi Germany prior to Dec 7, 1941. Neither I nor apparently the US government considered the sinking of a few merchants and even US destroyers in FDR's undeclared anti-submarine campaign a direct attack on the US or we would have declared war on Germany then

Yes, I failed to specifically include the phrase "...on US territory", but I am rather surprised that you do not read "..the US was not directly attacked" as something more than a few naval engagements with US losses, especially when I immediately that after pointed out that even FDR did not apparently see these as equivalent to direct attack on the US. I did not say "US forces" "US Ships" or "US assets". I repeat and I do not even need the qualifier: The US was not directly attacked by Nazi Germany.

 

[Shaby]

And what about the Atlantic Charter? What about the fact that both Germany and Japan were considered to be a part of the same coalition (as in fact they were)? What about the planning assumption for the two ocean war - which stated that the US should first engage and defeat the stronger power before defeating the weaker one?

 

[Michele]

I do not even need the qualifier

We'll disagree on that, as well as on the other inaccurate statements you made. My apologies if you felt insulted, that was not my intention.

 

[zoomar]

And what about the Atlantic Charter? What about the fact that both Germany and Japan were considered to be a part of the same coalition (as in fact they were)? What about the planning assumption for the two ocean war - which stated that the US should first engage and defeat the stronger power before defeating the weaker one?

The Atlantic Charter was agreed upon by the Roosevelt administration in the US and the Churchill government in Britain...and was intended to govern the joint policies of these two powers if and when the became allies in a World War.

If we presume a situation in which Britain is defeated by Germany before the US is attacked by Japan, one can't presume the Charter would still govern US policy after Britain is occupied. There are a lot of variables. It very well might, if the entire Churchill government including the Royals decamp to Canada or India and are recognized by the rest of the British Empire, but perhaps not if it is only a small exile force from the conquered British Isles that no longer has the ability to marshal the entire resources of the British Empire. A lot really depends on what happens in Britain and the Empire.

 

[Cronos988]

I disagree with most of what you are saying, especially with respect to the USSR and USA. You are aware that the USA only recognized the Soviet Union in the early 1930's, right?

I don't see how that is relevant.

I also trust you are aware that anti-communism was probably as prevalent in the 1940 US Congress and population in general as during the cold war. And surely you appreciate that, in 1940 or early 1941, when this imagined German defeat of Britain would have occurred, the USSR was in effect an ally of Hitler's Germany. The whole myth of "uncle Joe Stalin" and the fact of US/USSR friendship only developed after the US entered WW2 and it became necessary for propagandists to paper over the inconvenient fact that Stalin's Russia was almost as reprehensible as Hitler's Germany.

Yes, Stalin became one of the good guys when that was necessary for political reasons. Like it will be necessary following the inevitable Nazi invasion of the USSR which, I assume, still happens ITTL, as the only way to avoid it is an anti-Nazi-coup. And only few people where aware in the 1940 who was how reprehensible. Most information was propaganda, as evidenced by the fact that Mao's communists enjoyed quite a lot of support from the american public and journalists. Anti communism prior to WW2 is not the same as the anti-communism of the cold war.

FDR may have had some grand plans, but he had to use every legal and quasi-legal means at his disposal to assist Democratic and Capitalist Britain in 1939-1940/41, and this did not include going to war.

He managed, though, and Michelle has already given the relevant figures that show that public opinion increasingly tilted in favor of war. Also assuming that just because Britain is democratic and capitalist, americans will have a positive image of Britain is ignoring the somewhat "troubled" history of the two states. If we go by the sentiment expressed by a number of generals during the Anglo-American alliance during WW2, there was actually rather a lot of anglophobia around.

Only if the US was already at war with Germany when Hitler invaded the USSR can we presume that the US would adopt a friendly posture toward Stain and the Soviet Union.

And you are basing this assessment on - what exactly? Why would America not support the USSR against a german invasion? They did OTL, Lend-Lease was extended to the SU in October 1941.

Since it is reasonable to presume the US would not have declared war on Nazi Germany prior to that date (we didn't OTL after all) then it is highly unlikely FDR could get the US congress to go along with a declaration of war against Germany in alliance with the USSR.

And why do you figure would it been hard to get congress to extend the war to Germany when the US is already at war with Japan and significantly aiding the USSR via LL? At some point, the US is so involved in the conflict the declaration of war becomes a formality. Even if the US never declares war on Germany, American tanks will roll through Berlin, just with soviet crews.

Once Japan attacks the US, it's entirely up in the air whether the US would adopt a "Germany First" strategy - or even declare war on Germany if Hitler doesn't do this first. My own thought is that the US would eventually enter the Russo-German War but drive a hard bargain with Stalin...we'll help you if you help us in Asia (ie: declare war on Japan, give us air bases in eastern Russia to use against the Japanese, and invade Manchuria)

So, in the end, you do agree that the US under FDR will always eventually enter the war against Germany? I don't disagree that it likely won't be Germany first - with terrible results for Europe (first atomic bombs on central europe, then soviet occupation). How hard the bargain is depends on how desperate the Russians are. The german invasion will likely go a whole lot worse if the SU is prepared, so chances are the bargain will not actually be all that hard. OTL FDR believed that he could handle the SU in the UN post war, and Stalin was able to get him to agree to almost everything he wanted.