Don't think this is as straightforward as you make out.
So after 9/11 you would have done nothing? No Afganistan no Iraq? Perhaps you are sending the wrong signal to these fanatics? Doing nothing to combat terrorism post 9/11 would not (IMHO) have reduced terrorist activity.
Also are you saying that if we pull out of Iraq now as a result of these outrages it will reduce our chance of attack? I think not. Dont we become the target of any crackpot minority trying to get their own way or "convert" us to their brand of ideology?
I'm not saying you dont have some valid points or that there isn't something in what you say, it's just not as easy as some would have you believe. Once again my "beef" is with the armchair primeminister/president. What would you do or what would you have done? Not just Iraq, Afganistan, but Ireland or the Falklands or Hitler or.......