As it happens, there's another universe in the back of the closet next to the bookshelf in the spare room. It's nearly identical to ours, except that in this universe, 9/11 never happened.* Everything else is the same: George Bush, Barack Obama, Iraq, Afghanistan, Libya, Yemen, Guantanamo, Bagram, the torture networks, the secret prisons, and on and on - but there were no planes crashed into the Twin Towers and the Pentagon, no yearly donning of sackcloth and ashes by politicians at ground zero, no annual pageants of official grief.
In describing our own universe to the natives, I attempted to explain the significance of 9/11, how it changed everything forever, but they were frustratingly unable to comprehend. The United States, they said, had spent its time killing and torturing and enslaving the world before 2001, and spent its time killing and torturing and enslaving the world afterward as well; the only difference was the loss of some three thousand souls, an evidently paltry cost given the American government's valuation of human life.
I attempted to explain the situation to them again, and felt that I was close to succeeding, but our conversation was cut off by a NATO air strike.
*Inhabitants of this universe insist that, in fact, 9/11 did happen, and does happen, once a year, every year, right after 9/10 and right before 9/12.