Yes, but 2001 is not the only year in which terrorist attacks have been used as a weapon. They've been used for a very long time, and for maximum accuracy, the threat needs to be assessed with as large a sample size as possible. The actual threat of dying from a terrorist attack is astronomical. About the same as a lightning strike - and that's when you include September 11th in the statistics.
But even if you look at only 2001, the death rate from terrorist attacks was, as you said, about 1 in 100,000. The overall homicide rate in 2001 was 5.6 per 100,000. Yet, in spite of the fact that you were five times more likely to be killed in an ordinary homicide than in a terrorist attack, no one has suggested the government be given broad new powers to deal with the homicide threat.
As a matter of fact, we also don't know if the increased powers given the government, which some consider to be infringements of civil liberties, have not prevented further attacks.