History is key here. Most people know nothing about the history and so just buy into the farcical cartoon character that is North Korea. Remember that the US flattened North Korea during the Korean war. It also threatened NK ever since. As a response, NK has developed a military-first strategy to protect itself. Most of its defences and ability to survive lays undergound. A US strike, either conventional or nuclear, would be survived by NK. As for what happens to SK or US bases in Asia, or on US soil, is another matter.