At the time of the September 11, 2001 attack which got this new era of war started, the enemy in Afghanistan numbered only 400 men. Their closest acolytes spread across the region added another few hundred. The George W. Bush administration could have negotiated their extradition. Barring extradition, special operations forces and CIA Special Activities Division paramilitaries could have made short work of the small number of al Qaeda fighters, including Osama bin Laden and Ayman al Zawahiri, if only they'd been allowed to. The whole mess could have been over by New Year's Day.
Instead, regime change was declared in Kabul and Baghdad, and later Tripoli, Sana'a and Damascus. The combination of Bush's Iraq War II and Barack Obama's half-regime change in Syria even led to the creation for three years of the "Islamic State" Caliphate of W. Bush's old war propaganda and bin Laden's wildest dreams in the lands where the Baathists used to rule, creating another regime which had to be changed.