Iraq under Sadam Hussein was a nation under the thumb of a dictator. So is North Korea today. Both seem(ed) to me to be content to keep to themselves, harming really only their own people. The invasion of Iraq and killing of Sadam arguably opened Iraq up and created a considerably worse problem for other nations in the area, and for terrorism against the west. Would an invasion and displacement of North Korea on Trump's order do the same there?
I think you may be asking the wrong op title question. Really...don't you want to know if pre-invasion Iraq and N Korea have the minimum structural and US-relation things in common so that there could be similar outcomes?
Saddam was suppressing fanatics so he could remain in power. Some citizens were also radicalized by the war. Additionally, there were people in nearby countries who felt they shared something with Iraqis, enough to try to unify in a radical islamic state.
Korean dictator doesnt seem to be holding fanatics down, but instead brainwashing people. With his regime's removal, there might be more reasonable people. On the other hand, if Trump did something insane, like nuke them, he could possibly create sympathy and radicalization of neighbors, like family members in S Korea and sympathizers in China. I think familial ties may be a link and a long time ago, maybe ideology...but now China doesn't share that ideology with N Korea. N Koreans could learn to be economically successful and stable like the South. So overall I think there are less risks making a giant radical state for the Korean situation than Iraq, and if the regime were overturned slowly and peacefully things could turn out very well for them. Of course Trump could screw it up with a series of bad decisions regarding N Korea and China...