I think you give Bush way too much credit...hell, by some accounts, he was unaware that islam had different sects.
I believe we have an enemy: radical extreme islam. that enemy needs to convince the arab street that it has their best interests at heart. Saddam was a bad bad guy but, like it or not, he did a few things better than we have been able to do and we would be better off today if we had let him keep doing them: 1. he kept those same islamic extremists from gaining a foothold in Iraq (we have failed at this) 2. he kept sunnis and shiites from slaughtering each other (we have failed at this, and many middle eastern leaders feel that the carnage we have set in motion in Iraq may very well spread to Lebanon and the palestinian territories in a very short period of time....ooops) 3. He kept Iran in check vis a vis their aspirations for regional hegemony and dominance. (we have failed at this as well, and the mess with hezbollah in lebanon is proof of the growing influence of Iran in the region now that Saddam is gone). With Saddam gone, we have lost on several fronts and radical islam - and Iran - have been the benefactor of our fuckups.
All true, but it sounds like you would also agree that this was gonna come to head at some point. Saddam or no Saddam. Afterall he was still in power on 9/11 so it didn't keep Islamic extremism in total check. The questions are still then when and where do we want to fight this?
I would agree that I am probably giving to much credit to Bush as well. But planned or not the end result is similar. We are drawing large amounts of terrorists to one place, instead of them poking and prodding here and there across the globe.