To be honest,
I don't think either is a very imminent or real military threat to the (mainland) USA.
-Iraq lacks the range. While they are capable of attacking other countries in the region, if left to their own devices, I doubt very much they would do so. Saddam Hussien is aware that an Iraq attack or invasion on a neighbouring country would justify another US/UN intervention which would result in the defeat of the Iraq military and more importantly the end of his regime. Again, I doubt seriously he is willing to give up power. (If left completely alone, however, he would probably go back to eradicating the Kurds, which is why the no-fly zones should be kept in place.)
-N.Korea currently lacks the range and the arsenal. Even after another ten or twenty years of weapons development, they would still pose only a fraction of the nuclear threat that the Soviet Union did. In the current crisis, if war did break out, and they wanted to attack the US, at best, they would only be able to launch the one or two (highly innaccurate) missles they have at Alaska, and possibly Hawaii. They are far more likely to use their limited nuclear arsenal against Korea or here in Japan.
That being said, N.Korea does pose a very real threat to Korea and Japan. They have on many occasions threatened to turn Korea into a 'Sea of Flames' if war broke out. Their artillery alone could do this (Seoul is only about 60km from the border). It is estimated that over a million would die in the first month of a war on the Korean penninsula.
However, a second Korean war would lead to the total destruction of the N.Korean regime. There is no way they can win and they know this. The people in power in N.Korea, Kim Jong Il and the group of generals and high ranking party members that support him, are not foolish enough to risk losing their power and lives in a war they can't win. The N.Koreans can be said to be belligerent, bullying, and bellicose, but one thing they are not is stupid. This is why they will not make the first move.
In summary:
-Iraq poses no military threat to the USA. This is one of the reasons why the US is willing to invade in an attempt to displace the Hussein regime.
-N.Korea poses no military threat to the USA, but a great threat to Korea and Japan, and American interests in Asia. However, they are not likely to start anything. This is why the US is keen on using diplomacy instead of the threat of force. And unlike Iraq, the N.Korean regime is also very unstable. There is a chance that in another decade or so the country will either collapse in on itself, or peacefully reunite with Korea (much like Germany did). This is another reason to hold off from any military intervention.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
I encourage anyone interested in reading more about the past and future of global conflicts to check out a journalist by the name of 'Gwynne Dyer'. He writes mostly on this topic, and his essays tend to be very realistic, impartial, and well-thought-out. He is also very good at avoiding the kind of sensationalism and scare-mongering common to magazines like Time, and Newsweek.
<small>[ February 02, 2003, 08:30 PM: Message edited by: tsukaesugi ]</small>