I beleive that North Korea is going to be a 'threat' regardless of any action, or lack thereof, the west takes. If it wasn't 'Military Exercises in our waters' then they'd find something else to threaten America about. In the end, they are alot weaker than they beleive themselves to be. North Korea will continue to flex what little muscle they have until one of two things happen. Either the US will make a ridiculously overblown pre-emptive strike which will start a massive war, or the Korean people will revolt against their corrupt govornment and the counrty will descend into a bloody civil war. If anyone starts an international war, it will be the Americans.
In the end, threatening America or any of its allies with war is a stupid thing to do. North Korea is not a respected counrty in the east, and in any kind of war, they would find many of their border countries siding with the Americans.
As far as I can see, North Korea wants to let itself think that it is still a major world super-power. Unless someone at the top is utterly batshit bonkers, nothing will come of these threats. And that applies to both North Korea and America.