Two Ocean Navy Act passed right after Fall of France.
Or, more to the point, the Two Ocean Navy act was passed
due to the fall of France. With Germany left alone (Even momentarily before war with the USSR) on the continent. And this buildup persisted, and would continue to persist, throughout the war and until 1944, as after D-Day and the successful invasion the number of warships cut by the US was in the 100s - and further programs were cut later. Sans a successful toehold in Europe, the Navy is going to continue to expand at a monumental rate.
So even that alone shows how pointless a Naval War against the US Navy is in a Germany victorious timeline - even if the Germans gain access to every part of the British/French/etc Navies, combined with the Italian Navy... It'd not really be enough to even threaten. (let's not ignore how damaged the fleets would be in the aftermath of such a war as well. And let's ignore that at the least the British Fleet would have fled to the remainder of the Empire long before it'd defect to the Germans, even if they managed to not sink the French fleet (and it wasn't scuttled). By the time the Germans would have defeated the USSR/UK in such a world (as highly,
highly improbable/impossible that'd be, the US Navy would have reached a scale that the Germans couldn't cope with.
So, on top of that, the US is not embargoing Japan? Then that implies that the Japanese are not being as threatening as OTL. Because if they are, there isn't much of a reason that war doesn't break out. Sure, Pearl Harbor may not be launched, but the war drums were beating louder and the favorability of war was growing by the month according to the period polling data. Eventually, somehow, the hand would be forced. The scenarios have already been well explored.
So no embargo and war in Japan means that Japan has not aggressed outside of China, which means that the UK, and eventually the USA, will start protecting the former colonial regimes - the US far more interested in replacing the regimes, of course, than the UK would be in maintaining them. Aid would continue to reach China, and the war would likely continue for some time.
Let's not forget that, in the event of the capitulation of a nation to the Germans, their territory in the New World
would be occupied precisely to prevent the Germans from launching an assault against them. The nearest base for the Germans would be Brest in France (the Azores were to be occupied as early as 1940 under war plans to prevent their fall - in the event of Germany succeeding in conquering Europe, they certainly will be occupied precisely to prevent them from being used as a base.
So, let's picture our scenario. Stupid lucky Germans through ASB influenced dice rolls have managed to conquer everything by 1944/1945. They spend a few years and decide to launch an invasion in that time frame. And this is a German Fleet, accompanied by (likely) the Italian and French Fleets, who combined would have 1 aircraft carrier in 1941. Graf Zeppelin is not a carrier, it is an overengineered refit.
For that matter, let's just quote Plan Z, planned to be complete by 1948...
Type Projected Completed
Battleships 10 4
Battlecruisers 3 0
Aircraft carriers 4 0
Panzerschiffe 15 3
Heavy cruisers 5 3
Light cruisers 13 6
Scouts 22 0
Destroyers 68 30
Torpedo boats 90 36
Yes, 4 total aircraft carriers, of which the US would outnumber the Germans about 8-1. Not counting light carriers or escorts; that's basically near fleet carrier comparison there. Let's not even go into smaller vessels, at which point there simply isn't comparison. The Germans planned to have 68 destroyers in total by that time - the US planned to have 410 - along with even more DE to fight the submarine menace. The only projected numbers that might be close would be the battleships - without the Pacific war, the US would "only" have 17 to the projected German 10. With the cancellation of the
Montana, they'd instead be trading battleship hulls for even more carriers, which would doom the German fleet even further.
And this is on top of the Germans having to operate on the far end of their operational range - the French and Italian fleets are even worse off, being short legged and used to the Mediterranean. They'd be forced to steam to the US Coast, or some other territory, to try and invade, and where they'll have to bring their supplies and invasion army with them. If they try to attack the US shore, that also brings into account the harbor defenses, which outrange anything the Germans could hope to build in terms of gunnery. It also brings them into range of land-based warfare, and gives plenty of tiem for the fleet to intercept... That is, if the silent service hadn't taken care of them.
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To get this to happen, you need a US of Man in the High Castle levels of apathy, and where invasion of US territory provides a decided "meh" reaction. The US in 1936 was over 40% of global warmaking potential. Germany, the USSR, France, and Italy combined couldn't quite match that - and the US never maxed out its economy as did every other nation in the war. And with a head start on naval production, there's no way to for Germany to catch up. And as the US can deny staging points that even hope to be in range for a medium distance...