This is actually a rather good point by Rich Lowry:
Without suggesting any moral equivalence (obviously), al-Qaeda and the United States can be seen as having had a race in Iraq over who would most thoroughly alienate the Sunni tribes. We got off to an early lead as foreign occupiers who had made possible the rise of Shiite rule and — in response to the insurgency — killed and captured young tribesmen. But al-Qaeda eventually lapped us several times over. The Sunni sheiks may not like foreigner occupiers, but they especially don't like foreign occupiers who assassinate their leaders, insist on marrying their daughters, commit unspeakable acts of brutality, and prevent them from smoking and drinking.
We had entered Iraq as a radical force. When we allied with the tribes, we became a more conservative force, protecting the tribal way of life from those who would overturn and repress it. This turnabout — so crucial a part of the success of the surge — doesn't neatly fit into President Bush's freedom agenda.
Or our agenda. The tribes are our allies so long as we advantage the tribes. When their interests diverge from ours, they will turn on us, using our weapons and money and training to eject us from their lands. What we are is not so much a conservative force as a convenient one, which various sects and tribes and groups use when useful and fight when necessary. And so we pinball back-and-forth, abandoning strategies and declaring successes based on which Iraqi actors find our weapons and cash helpful at that moment in time.