i think that if they were to actually follow up on the threat, thefallout from the nuke would blow back in their faces. i don't knowthe details of blast radius but i know fallout from Chernobyl was alot more widespread than the city of Chernobyl
Again, this only strokes their egos. Which they in turn use to coerce us.
Kim Jong-un is establishing his bona-fides as a hard-line leader in the Kim Il-sung and Kim Jong-il tradition. The North will probably stage some provocation shortly, which will throw the US into an hysterical tizzy.
Considering the DPRK doesn't even have a deliverable nuke yet, we're acting as if they had a major arsenal capable of reaching American cities.