C66 - take your point re; spooks. However, there isa crucial difference; those ops were mostly run in/against other countries. They were not aimed at bringing about the murder of 3,000 people in the most horrific fashion. Latin american jungle peasants don't vote in US elections.
It is important to remember that no event since Pearl Harbour has had such a huge impact on the American soul and psyche - and that, when all is said and done, was 800+ miles off the West Coast. it hit the Seppoe ego, sure, but people were, literally removed from it.
This was right in the heart of the de facto capital, and saw the destruction of a building(s) which for me, was the ultimate symbol of American wealth and power. It is virtually impossible to overstate the impact this had on the American people.
as for why such a poor State response to the catastrophe - because they believed themselves to be invulnerable, my guess is that they were simply taken offguard. what I mean by this is that armies, airforces and air traffic systems are large and cumbersome things which, by their nature, tend to be very slow in cranking up the gears-especially when doing so for the first time.
this was a new world for them, so factor into that the usual Washington internal politics, and you have the perfect recipe for catastrophe.
I'd also point out the prez, veep and Sec of Stae were all out of town.