This is true.nope. not even close.
China, NoKorea, Iran, etc. could put up a stubborn resistance in their own backyard if invaded, but none of them really have the ability to travel anywhere else in the world and engage a foreign power (maybe in a supportive role as part of a coalition, but not as the primary actor). Russia has shown it can carry on a half-ass fight in Ukraine and the Middle East, but afaik they don't have globally mobile capability like the US military.
I'm not really worried about China in this current situation, anyway. I think they know NoKorea is a problem that needs to be resolved - they just want to get something in trade out of it.
War with nukes is terrifying because in 2017 there wouldn't be winner just a massive amount of death and planet destruction. The U.S had so much military power that any other countries defense is nuclear weapons and that's scary but unlikely to happen.