Well the big reason the US hasn't "moshed" all over NK is because they have nothing we want. They don't have any really significant resources that I'm aware of, and certainly don't have any oil. They're also right next to China, and China likes to keep them there as a buffer from American-aligned nations like SK and Japan.
Basically, both China and the US are probably rather worried about the situation there, because the NK leadership is so wacky and volatile; neither side actually wants to take over NK because that'd mean having to deal with their internal problems and a giant, starving population that's been fed crazy propaganda from birth about the divinity of their leaders. No one wants to deal with that problem.
Basically, both China and the US are probably rather worried about the situation there, because the NK leadership is so wacky and volatile; neither side actually wants to take over NK because that'd mean having to deal with their internal problems and a giant, starving population that's been fed crazy propaganda from birth about the divinity of their leaders. No one wants to deal with that problem.