Werewolf, you seem to think of the Iraq war as existing in a political/diplomatic vacuum. I'm sure you know better, but it's not showing in your reasoning. If we leave, and Iraq becomes a place where Islamic terrorists have free reign, it would be a worse place than before, when it was merely ruled by a regime that was terrorist-friendly.
That is one reason why we entered Iraq, not because of "Saddam's boys" specifically, but because a state willing to aid and abbet terrorists is no longer to be winked at, and Saddam had shown he would not be persuaded by negotiation. Other nations we may deal with differently, but Iraq received one last chance for peace, and then the hammer was dropped. Iran has a resistance movement that we were trying not to alienate, Saudi Arabia and Pakistan were deemed better as arm's-length allies than as occupied nations. And so on. There may be other nations deserving of the Iraq treatment, but Iraq was deemed the next swamp to drain. Perhaps we should have gone somewhere else, first, but there are still reasons to invade Iraq.
Iraq is valuable as a show of force to intimidate the rest of the region. Unfortunately, the ubiquitous "quagmire" perception has dulled that prong of the strategy, while the unfortunate release of the Abu Graib photos and other things best kept quiet has harmed the effort to defeat terrorism. (Yes, the investigation could have gone forward, and the world could have been informed of abuses at a military prison in Iraq, but that without releasing photos that do nothing but make the US look bad.)
Look at the resistance the "world community" has shown to the "illegal war in Iraq," and ask yourself if invading any other nation would have been any more popular. If we can't knock over an obvious monster like Hussein, how can we invade any nation on earth? And we've got to do some invading right now - war is like that.