On paper, the US military is formidable, huge, with carrier battle groups, advanced technology, remarkable submarines, satellites, and so on. What does this translate to in North Korea?
Military power does not exist independently, but only in relation to specific circumstances.
While America is vastly superior militarily to North Korea in every category of arms, the North has nuclear bombs. It can’t deliver them to the US mainland, but can to Seoul. Even without nuclear weapons, North Korea has a large army and large numbers of artillery tubes within range of Seoul.
So an American attack by air on North Korea, the only attack possible short of a preemptive nuclear strike, would offer a high probability of a peninsular war, devastation of Seoul, paralysis of an important trading partner –think Samsung– and an uncertain final outcome. The United States hasn’t the means of getting troops to Korea rapidly in any numbers, and the domestic political results of lots of GIs killed by a serious enemy would be politically grave.
The probable cost far exceeds any possible benefit. And Pyongyang knows it.
As Gordon Liddy said, if your responses to provocation are wildly out of proportion to those provocations, and unpredictable, nobody will provoke you.