We fought a major landwar in Europe and Asia 60+ years ago to eradicate this sort of evil from the world
Do keep in mind we did not get involved in either theater in a major way until we were attacked by Japan. Yes, we sent supplies to Britain and did some other things but overall we were content to maintain our isolation from the war until that fateful day in December.
I do wonder had the Japanese not attacked us, would we have entered the war? Would Germany have eventually invaded Britain? If Germany had been able to invade Britain, would we have entered the war then? Obviously we would have entered the war had Germany attacked us, but if Germany never went to war against the US, would we have been content to sit at home and let the Nazi murder machine roll on?
But that's really a subject for another thread...
Another factor is that back then, we fought wars to win them. We didn't give two shits about "hearts and minds" or rules of engagement...the only ROE was "march to the sound of guns and kill anyone not dressed like you". I think the half-assed way our politicians make us fight would be disastrous in a conventional war.
Not to mention that as discussed in a previous thread concerning NK, the population is hostile, brainwashed, and would need massive support. Plus then we have to deal with China.