This is one government crazy enough and capable of an EMP at back on the USA. Hello 1870’s. But, their country would be erased in retaliation. And, the Dear Leader knows that.
Yes, I am sure that dear leader, though dumb, is not stupid, and knows this. I am sure there are submarines patrolling only a few miles off the coast of North Korea 24/7/365, whose missiles could reach North Korea in about 30 seconds.