The US military in Iraq has put together a profile of the typical AQI foreign fighter. Spencer Ackerman calls him Mr. AQI and reports:
But Iraq wasn't what he thought it would be. Mr. AQI wasn't an infantryman, where he'd bravely stand and fight Americans, he was pressured into being a suicide bomber. Nor were his targets the Americans he wanted to hit -- they were the Iraqis he came to avenge. According to Colonel Bacon, in some cases, Mr. AQI was happy to be in American custody, where he would no longer cause Iraq any more pain.
Let that sink in for a moment. For Mr. AQI has a lesson for us. Counterfactual conditionals are always problematic, but in all likelihood, according to MNF-I's own profile, if the United States. were not in Iraq, Mr. AQI would be back in his taxi in Algiers or Jedda. Were it not for Abu Ghraib -- which, of course, never would have happened had we not invaded -- Mr. AQI would never have felt that it was his religious duty to kill Americans.
Personally, I don't think you should regard counterfactual conditionals as a particularly problematic class of statement -- assertions about causation can be transformed into assertions about counterfactuals and vice versa. Which brings us to the point. People join AQI to fight us in Iraq. Our being in Iraq isn't stopping them from fighting us "over here," it's causing them to fight us "over there." Iraq would still have lots of problems if we left, of course, but there's every reason to believe the al-Qaeda element there would be rapidly wiped out with its supply of new recruits cut off.