No. North Korea should fear you. America is the only country ever to have used nuclear weapons, it used them against a civilian population, and since then it has spent the intervening decades starting wars with every other country in the world which disagrees with it about ideology.

Well, we should give just a little care for North Korea as for these reasons:

- Their economy: a bunch of reports shows that this country can hardly have enough capital for a war. Even recently we heard that they implemented some nuclear experiments, do they really own enough threats to launch more than 1 missile? In addition, logistics would be the first thing to ensure during a war, which the U.S can easily destroy with air bases in our allies countries nearby.

- Tech: Nah, not many things to say about a country that still limits the use of the Internet. Yes, they DO own the nuclear power, but modern warfare contains much more. We have the pierce defense again foreign missiles. We have enough equipment and vehicles to block them in the sea (well if China comes into play, it would be a very very different story, but I believe that China would be wise not to interrupt too much, or at least they would give a hand in darkness)

- Political: I must claim that North Korea has nothing to do with a war. The most possible path is that Kim Jong Un seems to guarantee his position within the government. He needs something to gain pressure against the U.S, but not to climb into the second Korean war.

For those aspects, the U.S should not give a damn care (or little, if any) for North Korea.

N.K. simply wants an outside enemy in order to galvanize the people behind their leadership. They don't actually want a war, or at least they don't if they have any sense (and please note that the powerful individuals that prop up Kim Jong Il aren't stupid).

Que sera, sera ;)