You are absolutely right about the PRC.

NK may well be the PRC's pawn, designed to drawn US attention away from PRC aggression in the S. China Sea and huge trade deficits as well as China's theft of US intellectual property on a grand scale.

Also, NK could conceivably be a tool the PRC will use to destroy the US.  If NK attacks the US and causes catastrophic damage, then the US would be weakened to the extent that it could not oppose the PRC in the S. China Sea or anywhere else.

Since the US has sold the PRC trillions of USDs worth of debt, using NK to attack could be painful for China in the short term, but the PRC thinks in terms of 100s of years, so the short-term sacrifice might be worth it for them in the long term.

You may also be correct about Russia which feels threatened and betrayed by the US -- e.g. US radar in Romania & Poland contrary to earlier US promises.  Putin may believe than most enemies of the US are friends of Russia.

For the US, NK presents no good outcomes.