As far as N. Korea ICBM's go, the latest updates I read put their Taepodong missiles as possibly having the capability of reaching Hawaii or Alaska, barring any malfunctions in propulsion or guidance. They are upgrading these missiles and the next upgrade is thought to have the capability of hitting the U.S. west coast.

The problem is, NK has to create a nuclear warhead that will fit on these missiles and actually work. That is a whole other endeavor in and of itself.

I think a more likely scenario would be a "missing" NK sub having a nuclear bomb aboard. The sub sneaks close to a coast or a port and then detonates, the seamen dieing in the name of NK and Kim jIl.