The USA have to watch out for another imaginary enemy they build up like they did with Iraq. This resulted in the widely destabilized middle-east we know today. We should see the DPRK's posturing simply as such, and not as a serious threat. Sure, shooting a missile over Japan, and the constant verbal threats of war is bad, but their ability to project power is very limited. We should worry more about a suddenly collapsing North Korea, which could result in civil war and a catastrophic famine. Remember how most ppl were surprised in the quick dissolution of the UdSSR ? This is bound to happen here as well, and then China and the West have to act very fast to prevent a massive humanitarian crisis.