Why is the US just sitting by and watching this happen?
The German invasion of the USA whether it be throuhg South America, North America or canada would never succeced against the superior naval powers of both the surviving Royal navy (which, seeing the fall of Britian would have evacuated) and the USN. Germanys Battlecruisers and Pocket Battleships are no match for a US Battleship one on one.

The USA would probably build a german type wolfpack and use them to harass the German sea lanes both for convoys travelling to Britiain, and surface ships both redeploing to their combat stations and the constant patrols needed to denfd the entire english channel and medeterrainen area's.

Ok here is one, What about the man shortages the Germans faced? the losses with the long battle that would have happend against both the British and Russian armies, especially the losses sustained in Operation overlord.

Now how are they going to find the men to manage all there captured territories, to fill there ranks in the Kreigsmarine, which will have to be expanded hugely, as well as the airforce and of course the men needed for the actual invasion of america?

In your secenario do the British hold North Africa? if so there is the launch of point of the invasion, or if not that, with the fall of japan, through south-east Russia, the long way put pribably the only way.

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