I would stress it this way: thousands were killed because we did not comprehend the nature of a suicide mission. Prior to 9/11, if a plane were hijacked, pilots and cabin crew were trained not to resist. The underlying assumption was that the hijacker wanted to live. Better to land the plane safely- no matter where than potentially causing a problem in flight.
9/11 changed that paradigm.
It's a lot broader than that. For the last several decades, Americans have been indoctrinated to submit to any authority rather than resist.
I mean look at the responses on this thread to an American who is resisting (peacefully) authority.
I can guarantee you that if I flew again, I'd rather be seated among 100 passengers with the mindset of this "free stater", than 100 passengers with the statist mindset of many posters here. The former would likely resist a hijacking. The latter would likely not resist.
9/11 changed that paradigm.
For some Americans, it did. The statists in DC still don't get since they are blocking the armed pilots initiative passed by Congress.
As a program also pointed out, if it were not for the horror of 9/11, one couldn't come up a better plot for a comedy. There was...you pick the word: stupidity, bias, negligence, derilection of duty, misfeasance, malfeasance, etc. at every level of our government leading up to that day; especially relating to intelligence, immigration, and law enforcement to name a few.
The morons in government just don't get it. Remember the 'Profiling' issue in the aftermath?