1) this does not seem remotely likely, as all three countries would be quite a bit worse off, no matter what. But then, pretty much all participants in WW1 wer

1) this does not seem remotely likely, as all three countries would be quite a bit worse off, no matter what. But then, pretty much all participants in WW1 were worse off afterwards, even on the winning side, so lets pretend they get exceptionally stupid and a war happens. 2) if the war is being fought in Asia, the U.S. loses. Land wars in Asia are hard to win for anyone, but especially when you're an ocean away from Asia. If the war is being fought in the western hemisphere (i.e. China and Russia are attacking to try to conquer the U.S.), then the U.S. wins. If it's being fought in cyberspace or outer space, then there isn't ever really a resolution, just a lot of nastiness until eventually a truce of some sort happens. 3) the fact that point (2) is well known to all three country's leaders, reinforces point 1. And, thank goodness.