Bill wrote:
Something about the war on terror seems different though, and I can't quite put my finger on it.
Could it be fear? Fear for the USA on 9/11 - for the public and most institutions - of a successful attack by an enemy unknown to them. An enemy then thought to be capable / considering further attacks.

Nation-states rarely react well to a threat that appears to upset the assumptions made about public security threats, i.e. a minimal risk to the population and normal society operation. Public, not national security. Even more so for the USA which via geography and power - to name two - that has kept such intrusions at a distance.

AQ was a largely unknown enemy after 9/11 and the USA, plus many others reacted often desperately to gain more information. Using methods it normally would avoid. We did exactly the same in the early year of 'The Troubles'.

What is the quickest and easiest political response to such an attack, with due allowance made for that simple motive revenge? "Find 'em and kill 'em".