Seriously, people who don't understand why 9/11 still deeply impacts the American psyche don't really understand the American psyche itself. Americans have always had a sense of invulnerability; not only are we an extremely wealthy and powerful country (arguably the most powerful country to have ever existed), we're extremely geographically isolated from the rest of the world save for Canada and Mexico. While the European psyche was deeply scarred by WWI and WWII, America remained relatively unscathed (aside from Pearl Harbor). The last war we had on our soil was the Civil War and it happened well over a century ago.
9/11 was (and is) such a huge deal because it was the first time most Americans felt a sense of vulnerability. The World Trade Center was a symbol of our economic might, and terrorists completely razed it to the ground. Plus, remember, while Pearl Harbor was a big deal, it targeted a military base. The 9/11 attacks struck a civilian target and all those who perished were civilians or first responders, not military personnel.
I agree that we shouldn't make an enormous deal about 9/11 and that the War on Terror has been a total clusterfuck, but it honestly pisses me off to see people try to brush it off and claim that Americans are overreacting. I mean,
3,000 people died; even the most horrific terrorist attacks since rarely break triple digits (thank God). Plus, you have to remember how shocking it was that the attacks utilized planes; before that point, nobody ever considered airplanes being used as weapons (I mean, there were kamikaze pilots, but that was decades ago).
Oh, and I came across this clip a while ago that really reminds you of the horror, shock, fear, and confusion that 9/11 caused. It's a video that two college students shot from their dorm. It starts up in the aftermath of the first strike, when people were still thinking that it could have been a horrible accident. Then the second plane strikes and all hell breaks loose.