North Korea have nukes and
delivery systems that can reach DC. Even discounting the nukes, they have a huge and well-disciplined armed force, nothing like the demoralised Iraqi Army that the Yanks rolled over two decades ago. Oh, and they have massed artillery batteries aimed at Seoul right now that can level the entire city within hours. Plus it would drag in the Chinese by basically taking the Korean War off pause.
Anyone arguing for the invasion of North Korea has no credibility to reduce in the first place. I doubt that the Yank brass has any real desire to stick their cock in that particular hornet's nest.