I think there is a big difference between the powers that committed those atrociticies. Japan was behind Pearl Harbor wheareas a scraggly fundamentalist group in the middle east was behind 9/11 attacks. The former was a full blown exercise of military power and neutralization of some half of our naval fleet in the Pacific. The latter was a targetted terrorist attack largely organized by one main guy. We got the guy, and we could have probably gotten him without 20 years of war.