North Korea would crumble on itself without mountains of support from actually profitable nations.  They wouldn't stand a chance against the full might of the US, not any more than a sick child stands a chance against a roided young Mike Tyson.  Only thing they might be useful for is as a martyr for China & Russia to have an excuse to retaliate.  North Korea is not a threat to anyone, let alone the US, if not a threat to themselves.