Warbler said:

NKorea vows to cancel Korean War ceasefire

this is not good. Just how hard would it be for the US to take over NKorea?

It would likely result in many deaths. Though Korea has some nuclear weapons, they don't have a proven capability to launch them far if at all. They could try to hit South Korea or China or possibly just use them in their own country if they realize they are going to lose. Rebuilding the country and locking down all the nuclear weapons would be a ridiculously huge job in any event.