"In retrospect, invading North Korea in 2003 would have been a far better choice than Iraq."

Yeah. Sure. With Seoul in range of NK artillery and poison gas grenades. By the way, do you know why NK still exists and will exist for a very long time? Because it has 2 boarders with superpowers, China and Russia. And both powers have zero interest that the US soldiers, stationed in SK, move close to their boarders. Invading NK looks easy on paper. But the long tail risk is enormous. Do you know why 2 Korean states exits at all? It was not the North Koreans that brought the US army to halt. But yeah, for sure this time the Russians and Chinese won't bother.