It just wouldn't happen. A landing in America wouldn't work at all and a landing in a United Europe wouldn't happen. So therefore the war wouldn't even go on to be anything other than political crap. Unless you have the nuclear option their really isn't anything either side could do. As for the navy, yeah sure that could happen and the U.S. would probably win and anything in the air would only be bombers and even then it wouldn't achieve much except damaging military bases and killing civilians. If it was in the air the U.S. would probably be able to maintain its air space and do some damage with B1's but this situation doesn't make any sense and it wouldn't accomplish anything. So overall the entire situation wouldn't make any sense and it wouldn't happen in the first place.