Hmmm!? What is clear is that enough was known to prevent it.
Without the "Patriot Act" or anything else.
And if the information didn't "rise to the level" of awareness or concern of the authorities, what WAS rising to the level of their interests?
And the NSA - "Who would have thought terrorists would fly airplanes into buildings" is so incompetent as to defy imagination. Lots of people had thought of that, who weren't National Security Advisors. Who should have.
Arf