Together with Canada, many of the islands in the Caribbean which are still in European hands and the islands shown above (including Danish Greenland) which are also in European hands (British and French). That means that American troops would be cut off on day 1. They would be in Europe, surrounded by enemies, with sea lanes controlled by their enemies and no possibility to either replenish or supply them. And evacuation ? No we will just annihilate them and that is something President Bobby would have to explain to Congress. Plus -we would have the propaganda on our side: we just need to compare you to the likes of Nazi Germany and we can do whatever the hell we want. "For the time since 1940, our country has been under attack by a fascistic power !" Those troops will be dead in 48 hrs max. And by that time real global powers will move in.