North Korea is woefully unequipped for war anyway. Its army is relatively small, and public opinion for the current dynasty is falling more and more each day, as more families are stricken by starvation or other basic errors on the leader's part. Indoctrination in the country is powerful and will go a reasonable way, but North Korea's troops would be, for the most part, unmotivated. Not to mention inconsequentially small; America's population is over 15 times that of North Korea.
A nuclear war would be devastating worldwide, but the one country who would definitely be hit hardest by any kind of nuclear war would be the instigator. Kim Jon Um, for all his shortcomings, isn't stupid, and he knows this. As such, the notion that he might actually use these missiles is absolutely tiny. Don't forget that N. Korea actually declared war on America I think a few months ago, and not a single person has died yet as a result.
Just think of N. Korea as the passive aggressive old guy across the road who shouts threats at you as you walk down the road for no discernible reason, bu the most he can actually do is throw a rock in your direction.