There weren't any Afghanis on the planes of 9/11 any more than there were any Iraqis. They were from Saudi Arabia and the Gulf States, and they got their flying training in the USA. Two out of the 19 involved may have had some training in a camp in Afghanistan back in the 1990s.

Attacking Afghanistan was a gesture, an exercise in public relations seen as politically necessary in the wake of 9/11. There is good reason to believe that the Afghani leaders could have been persuaded to hand over Bin Laden, but that wasn't the gesture which was required by Washington.