Do try to remember that. CR is correct. This was not a "declaration of war". This was a criminal act of mass murder. Immediately after the fact, we had a choice:
1) Leverage the world-wide sympathy we had to illicit the help of the world's criminal investigative powers to root out the co-conspirators, bring them here, try them, convict them and send them to prison for the rest of their lives (similar to what we had done during the Millenium threat and the first group of thugs that tried to blow up the WTC).
-OR-
2) We could become just like the terrorists we were trying to capture while simultaneously alienating almost the entire world in the process.
Guess which one we did?