Development of an accurate and reliable North Korean intercontinental ballistic missile is a concern to be sure, but a bigger threat will loom when they can successfully field a fairly compact (the size of a minivan would do) nuclear warhead or "dirty bomb" device.   Consider:  Hawaii's law enforcement entities, U.S. Customs and Border Protection, plus the U.S. Coast Guard are incapable of interdicting every, or even most, of the shipments of illegal fireworks heading here every year (even after decades and decades of training and experience).  So at this point in history I have less concern about a North Korean ICBM than a nondescript container ship or freighter moored alongside a Honolulu pier.  It really doesn't require a fancy-schmancy delivery system to vaporize (or render uninhabitable) a good chunk of urban Oahu.