Russia has less military power than the Japanese and they're not communist anyways.
China would never destroy its economy by going to war with the US.
I'm pretty sure in terms on man power, Russia is second most powerful next to U.S.
In terms of Nuclear power, Russia is at the top.
China comes in third place with man power.
U.S. can't stand a chance against Russia and China. But it's not like they need too. If North Korea pulls any sort of attack on the U.S., China and Russia have to come in and stop North Korea.