Eight years ago, Barack Obama was a state senator from Illinois. Now the world wrought by 9/11--an America with two wars to prosecute--is his. He's the president we've had since 9/11 who isn't named Bush.
Obama's world is so fluid. If someone had told you in the fall of 2006, when Americans were dying in Iraq and the Democratic wave began, that three years later Iraq would be relatively calm and we'd be talking about defeat in Afghanistan you'd have been amazed. Three years ago, the left loved to tweak George W. Bush about not finding Bin Laden. Now, they don't bug Obama about the same failure to fine a 6'5" man with supposed dialysis needs.
The Pentagon's was rebuilt in a year and New York still has a hole in the ground. The federal government was reorganized at the insistence, largely, of Democrats who pushed for a Homeland Security department. Now, it's hard to imagine that the behemoth won't be broken up sometime down the road.
The Patriot Act and other laws born of that day have been tweaked but the larger civil liberty questions remain. Guantanamo Bay is still a prison and the U.S. will continue to struggle to deal with combatants who aren't traditional POWs.
Every president for the foreseeable future will be shaped by 9/11 just as the presidents of the last century inherited, say, the Cold War and chose to fight it in their own way. The day is still a tragedy still but it's now an inheritance, too.