Assuming (and this is a huge assumption) Georgia can win out and win the SEC championship with our loss to Bama as our only loss:
I've been going over scenarios in my head and, assuming we can do our part and win out the rest of the season and win the SEC championship with only one loss, the team that is actually the 800 pound gorilla in the room right now is Penn State, of all people. They are the team that is most likely to keep us out of the national championship game if we win out, as they only have one big game left against Ohio State. If they beat the Buckeyes, they'll probably go undefeated in the regular season, which means they would play the Big 12 champion in Miami for all the marbles, assuming that the big 12 champ is either undefeated or has only 1 loss.
USC, I'm not too concerned with. A 1 loss SEC champion will pass a 1 loss Pac-10 champion in the BCS because of strength of schedule and the extra game. A one loss SEC champion won't be able to knock a 1 loss Big 12 champion out of the BCS though.
Bottom line is that if Penn State is undefeated and the Big 12 winner only has one loss, the Dawgs won't be in the title game.