Sandman is smart, not a smart ass.
There are plenty of countries capable of hitting the US with a variety of weapons. China has the warheads and delivery capability, and so do many of the former Soviet states, still with targeting info set for the US. Pakistan has nuclear weapons.
This game has been played on the Korean peninsula for half a century. It's just the way it is.
A state of war still exists and the demarcation lines on land and water are the place where strength of will and posturing to scare the bejeezus out of the guys on the other side of the fence are the rules. Make the other guy believe that you are the bigger, meaner mother with a hair trigger.
Incursions are made, shots are fired, people die - all part of the unique dance on the peninsula.
Of course the North Korean military is fanatical in their devotion to their cause. Isn't that what all military are, or strive to be? Fearless and invincible? Isn't that the political strategy for any leader of any country? Get the population waving the flag and defending the notion to fever pitch that they are a chosen nation filled with the smartest, bravest, most righteous people defending their way of life as the best on Earth.
The bone-headed "axis of evil" speech changed the dynamic of the peninsula and played right into the hand of Kim Jung Il. Here was a label on the world stage that singled out North Korea with Iraq and Iran. The first one on the list, Iraq, was invaded and the other two were handed a golden opportunity to claim that they would be next. Why wouldn't they be next? What the hell else could they do except further arm and defend themselves from invasion?
They were handed the opportunity to say to the world, "You threatened us and we will defend ourselves." They were given the opening to overtly declare their nuclear intentions and can easily say that they have every legal right to test missiles, or even test their nuclear devices. They can claim they have a moral obligation to defend themselves.
A two bit tyrant son of a tyrant was given the chance to elevate his stature in the world. A few years ago, North Korea was the nation most disliked and least trusted in surveys around the world. They were displaced by Iran last year as Iran began to assert itself in response to being on the evil list. Maybe they can work themselves into the top spot again.
Politicians from all countries involved or near will find a way to maximize fear out of this, with the press being a willing accomplice.
(By the way, Charon, US forces are not in any country because the US cares deeply about the people of that country. US forces are in every country they are in for the political self interest of being there. The "We are your Savior" card doesn't play well anywhere.)