The capacity and capability of North Korea to act on its threats has proven time and again their ineptitude in the matter, both short, medium and long range. This does not mean they do not present a threat, in that they could initiate a war by attempting a launch, but a true nuclear war is unlikely, namely because of the massive technological advantage employed against them. It also needs bear mention that Mutually Assured Destruction is not the current policy or the objective one either by the United States. Even if, and I do phrase that as an if, North Korea had the capacity to reach out on an attack and hold a continental United States city at risk, the odds of that weapon landing on target are extremely unlikely for a number of reasons. There are a number of factors that reinforce this, just from the basic science of it, to the quality and state of the platform it is on, the weapon itself and yield, to just the target, barring of course the myriad of assets the United States has developed and maintains, the majority of which were built to combat a far more advanced adversary.
Again it is important to note that this does not mean they are a non-threat, just the reaction of the general public is not well informed on the matters of the arms at hand. The real people at risk are the South Koreans and the Japanese, because those layers of complexity are significantly reduced just by proximity alone and a few associated issue of politics and culture. However, the notion of "damaging the alliances" is ill informed. Proliferation does not remove credibility, it reinforces it. In essence, the North Korean dynasty is incentivizing and building upon those bonds and making it a matter of consideration for their enemies.
For too long has the United States neglected to continue building its fundamentals of deterrence, both horizontally and laterally. It helps none that the average person, speaking to just the United States, is afraid and uneducated on nuclear warfare, ionizing radiation, effects there of and home nation policy. This is why the North Korea ordeal appears as frightening as it is despite being more sound over substance.
