Also when you say Iraqs military caused us problems I have to chuckle. Not they didn't we ripped through them, destroyed them, and then let ourselves get dinged for 7-8 yrs policing the country. That was terrorism not the iraqi army.
No standing army can hang with the USA. You put 10 thousand troops together, 100 tanks, and you will lose them all if you go up against us. We will shoot down all your jets, own the skies, then drop fuel air bombs on your dug in troops. China, Russia, the only 2 countries with the technology and power to hang with our military.
We could reduce N Koreas military to nothing in about 3 months i would guess. Hell we would sink probably 90% of the navy and destroy all the airfields in the first couple weeks.
The problem is the result would be a Seoul laid to ruin because we can't take out all the artillery very quickly. It's the civilian casulties in S Korea and if China would stay out of it that are the major concerns. Not that we would have to put boots on the ground. They have no oil or major arteries the world needs for commerce. We could let them rot after.