I have been following various newspapers and periodicals (both online and offline). There is absolutely no possibility of war between the USA and North Korea. The experts of International Relations know very well that North Korea has been threatening to nuke the USA for the last twenty years, but the international community takes this threat with a pinch of salt. Further, the third big player in the region, i.e. China also doesn't want war in this region. North Korea can't act against the wishes of China.
Of late, I have been observing questions on possibilities of war between India and China, India and Pakistan, the USA and North Korea, the USA and China and between North Korea and South Korea. In another website, I have been continuously replying this type of questions for last one month. For all people, I would like to state that for every country, war is the last resort. Moreover, according to the theory of International Relations, war signifies failure of diplomacy. As the diplomacy has not yet failed between any of the above countries, the possibility of war is almost nil. However, there will always be threat of war (by immature countries).
We should not unduly worry in this regard.
Non-violence is the greatest Dharma; So too is all righteous violence.