Oh absolutely the west would love to effect regime change in North Korea. Morale win, keep the military industrial complex going, grow the economy, get rid of some pesky poors in combat, maybe hoover up some natural resources.

The problem is China, NK is strategically important to them as a source of said natural resources and as a buffer zone against South Korea. Plus lots of slave labour, global economies can never have enough of that.

So yeah, messing with North Korea means messing with China. Despite a lot of trying nobody has been that stupid yet.