I clicked other, though I would also point out that there HAS been a domestic terror attack-the shootings at the El-Al counter at LAX on July 4, 02.
But there has been nothing major because
Our security has improved so there are fewer good targets.
The men responsible for the next three major attacks, the "Lakawana Seven", Richard Reed, and that hispanic prison muslim arrested in Chicago for trying to build a dirty bomb, have been caught.
The big leadership and the money men are on the run because of the Afghanistan and Iraq invasions.
Lots of their cash has been seized.
The oil Sheiks, seeing our reaction, are not as forthcoming with cash and other assistance-this sudden parsimony is probably why they bombed targets in Saudi and Morrocco recently.
All of these contribute equally for preventing a second major strike.
But it is well doucmented that our security arrangements are far from ideal, and not all terrorists and their sponsors are accounted for.
So a new attack will eventually come, but they have been disrupted enough to keep them busy for that last 18 months.