Missile defense is a new untested technology. Moreover, it works best with Soviet-type ICBMs with spin stabilization that are quite precise in their aim, because it has to project ahead of the missile in order to strike it. North Korea missiles are cruder and have much less precise aim....because of their variable wobble, they are much harder to hit in a missile defense system. At least that was the situation a few years ago.
From what I've read, it is still the same. Now, I really can't sleep for thinking about it.
We need to be spending money on refining the system. We need to stop screwing around in Iraq and get on the ball.