nope. In beta, you could get the US to join the CP. That was changed prior to release. If the US gets to 100% CP, they reset to 99% CP. The only thing it does is delay the US entry into the war. In 1 PBEM, a game ended with the US still at 50% CP alignment. So no USA troops in the war.
Remember - The beatings will continue until morale improves.