You are assuming that North Korean nuclear weapons can be successfully deployed against the USA. I doubt they are accurate enough to get anywhere close to a target as small as Guam, but if they were to do so, American defences would shoot the missile down, and then retaliate in the knowledge that “China should stay neutral”.
I think the Chinese announcement has achieved two things:
- Given Trump the green light to retaliate to a North Korean attack, and
- Made it very unlikely that the Kim regime will attack any US territory or Ally, without the Chinese Nuclear deterrent to hide behind.
Just in passing, I view the position of the USA in the world as being more like the World’s Police than being an “Apex Predator”. America has always been at its best when protecting democracy and freedom from aggressors, and should never act as a predator in world affairs.
China is actually acting as the ethical voice at this time, surprisingly so for a totalitarian dictatorship with a lousy human rights record, and a usually aggressive posture towards the west, and its Asian neighbours.