WW2 Germany, USSR, and Japan vs. Current United States, who'd win?

How are Germany, the USSR, and Japan going to achieve either 2 or 3? Their combined naval strength (even assuming they get every single ship they had at any point in the war) isn't even enough to compete with a single U.S. Navy carrier battle group, of which we have 9, and we'd have ample warning of their coming.

Even if they get onto U.S. soil and somehow remain supplied, they now have to somehow compete with 1 million U.S. soldiers, each of whom are far better trained and equipped than their opponents and supported by far superior armored vehicles and artillery. They couldn't hope to compete with the U.S. Air Force, which would devastate them from the air and wipe the skies clear of their aircraft without loss (enemy aircraft would be destroyed long before they can even see the American aircraft). Frankly, the biggest problem the USAF would face would be ensuring the fighters have enough air-to-air missiles, but a better program would be to destroy enemy air bases and factories from the air (again, without any chance of losses).

Enemy forces are totally outclassed in every way - the only thing they have going for them is that the U.S. Navy doesn't currently have the transport fleet to send an invasion force to enemy territory (but one can be built).

Without the Russian military might the American public would have grown weary of war and settled for peace agreements.