Yup, I'd make mention of the Gulf War/ War on Terrorism. I'd possibly even consider having the players get involved in a mission, especially if there were super powered foes to fight. I'd maybe send them on a rescue mission, rather than have them involved in the actually assault on Iraq.
However, my campaign is about to return from the Ice Age adventures tomorrow night, at approximately the correct date, which is now 2000. So 9/11 hasn't even happened yet!