Did anyone else notice the flag materializing itself and making a computer-like sound ala Assassin's Creedafter the bell fell in front of Booker? We see something weird like this again when Booker takes the rifle from the barrel next to that crazy patriot. Is Columbia a computer simulation?
We also see lots of weird things happening in the trailer. The woman sweeping her burning house, the crazy patriot giving a speech to nobody, a paper deliverer riding a broken carriage with a lifeless demeanor. Maybe Columbia is a malfunctioning computer simulation of sorts? It certainly seems "off" for reality.
Study the gameplaytrailer carefully: