Well, France would be in basically the same boat as Italy, I imagine. Arguably worse because as you describe things, France would have been perceived as an outright turncoat against the western alliance as opposed to Italy which began the war as an axis nation and turned coat the "good" way.
True, but in the end, it's not like the Allies could have treated Italy much worse than they did IOTL, and that standard would apply to France. Of course, no permaseat in the UN, no occupation zone in Germany, no separate status for Saar, the same military limitations as for Germany and Italy (i.e. no nuclear France). OTOH, political and military European integration alongisde the econimic one would most likely succeed in the 1950s, if the French are in the same boat as the Germans and the Italians.
A lot would also depend on whether the Vichy regime was deposed as was Mussolini's government upon an allied invasion of France. In Italy's case, the fact that the King immediately lent his support to the new government immediately legitimized it as the only real government of Italy, even though the German rescue of Mussolini allowed them to set up a puppet regime in the north. Something very similar would have to happen in France.
Very true, but just like the less radical fascist and philo-Nazi top adies of Mussolini could backstab him when the military situation went down the tube, so the equivalent in the Vichy regime could easily do the same.
Also, as opposed to Hungary and Romania (whose initial allegiance to the Axis could be interpreted as the almost necessary response or minor powers to being in the shadow of German power, France was a major power, and such a switch of allegiance could have a major impact on the overal balance of power and direction of the war. In this TL, if Germany had gained an actual advantage (such as if Vichy permitted full German access to their north and west african bases and/or Madagascar to support the submarine campaign, the French joined the Axis campaign against the British in the Med and North Africa, or if initial French resistance to Anglo-American nvasions of north african and metropolitan France was stiff), there would be few among the allies willing to cut France any slack. That's not even considering the Soviet reaction if French forces joined in Operation Barbarossa.
Well, what the Soviets think is not going to be any relevant in the end
(just like it wasn't for Italy), since the Anglo-Americans shall be the only ones having boots into France. But otherwise, you make a most valid and interesting point, Vichy contribution to the Axis would a significant factor and could change the equation for the Axis significantly in 1940-42. Developing your argument, I can list some of the most relevant ways it cna change the course of the war, IMO:
I honestly lack sufficient WWII naval expertise to judge how much U-boats would be more effective with plenty of bases in North and West Africa (I think that Britain would manage to seize Madagascar soon afterwards French declaration of war, too close to South Africa). On a hunch I would say they shall not be a game-changing factor, but I could be mistaken.
In the Mediterranean, however, the picture is rather different. The Regia Marina and French Mediterranean Fleet combined could most easily get the upper hand and wrest control of the Mediterranean from Britain. Malta would most likely be switftly lost, French contribution in North Africa would most likely make Britain lose Egypt in 1940-41.
In the worst case scenario for Britain, they could face the "perfect storm" of the I-G-F Africa Korps conquering Egypt and preventing the fall of Ethiopia, Axis troops flooding Syria by air and sea (if Britain fails to conquer it beforehand), linking with philo-Axis forces in Iraq and Iran, and kicking the British out of the Middle East. With Britain still lacking the cobelligerance of America, and the demoralizing effect of fighting all of fascist continental Europe, the loss of North Africa and the Middle East could quite easily cause the downfall of the war coalition in Britain. If this happens, end of story, at the very least the Axis can exhaust isolated Russia into a Brest-Litovsk peace.
Even if this doesn't happen, Barbarossa would have a rather different course if the Axis could strike Russia from the Caucasus, too.
And even if the Axis only manages to conquer North Africa, and fails to get a real advantage during 1941 in Russia, French troops could quite likely give the Axis the extra boost it needs to conquer Stalingrad in the early phases of Operation Blue. As a consequence, Russia would be cut off from the Caucasus oilfields, and its war effort would be in deep trouble. Likewise, Russian counterattacks in late 1942 and during 1943 would be much less effective and costly. Mid-late 1943 could easily see relatively exhausted Russia facing a strong Axis entrenched on the Don, if not the Volga, and still making a credible threat to Moscow. A plead for a Brest-Litovsk separate peace would be absolutely likely, and assuming someone talks some sense in Hitler, it could be accepted.
Without Egypt, with Axis forces manning North Africa in numbers, and with the Italo-French fleet patrolling, the success of Torch becomes far from certain.
Anyway, if Russia bails out, and with Axis France, a successful Allied landing in France or Italy becomes ASB nonetheless. The Western Allies could conceivably land in Norway or Spain, and seize a good chunk of it before Axis successful counterattack owing to crappy logistic, but they would absolutely fail to achieve a strategic breakthrough towards the core of the continent before they get bottled out and stalemated for the same reason. The WA would be forced to kill time until they get the nukes.
It is quite possible that FDR would pressure for gambling everything on a rushed landing on the continent. With the demoralizing factor of Russia's bailout, and if the WA keep reaping bloody failures in their assaults on Fortress Europe (not to mention the fact that after Russia is out, the Axis can redirect its war production on air defense, making the Allied bombing offensive less and less effective for growing casualties), a collapse of the will to fight in the Anglo-American public (which doesn't have the slightest idea the nukes are coming) during 1944 is quite conceivable.
French contribution is not really going to change anything about the war in the Pacific. But in Europe it would quite possibly, if not most likely, to change the equation enough for the Axis that at the very least the Allies are stalemated and forced to wait for the nukes as a gamebreaker, at the very most win the war for the fascist coalition. Germany, France, and Italy getting nuked does not make for a pretty picture. But on the other hand, the Western Allies would be the ones to free Eastern Europe, which would be spared the scourge of Stalinism.
