The west has made some major mistakes when trying to police the world in the past. It is not our job. We have created a lot of our own enemies. And did you know that most of the map of the world was drawn up by europeans that were ignorant of how differant peoples were dispersed in specific areas. I am not isolationist, but I do not think we need to go after every single problem. The issue is, that is how super powers fall and lose all their money, they begin policing. At the moment the US army is stretched pretty thin by its standards guarding iraq...no way are we up to taking somthing else up.
We also have no right to establish mass cultural change...
On top of that, the war with Iraq wasn't just to kill Saddam. Iraq gives us another base and vantage point to look over the middle east. The fact is that middle east has a decent amount of power, as where sudan doesn't. I'd love to go and help Sudan, and you are right there are plenty of things we should and can do without using a pure american force and using the UN. The fact is it isn't going to happen...people rarely do anything to help or be nice, we are human, and we keep our best intrests in mind.