The common people in warring countries used to go right back to normal trade and travel as soon as their governments signed peace treaties. That doesn't seem to be as much the case now.

Although I do agree with you about the fundamental differences between Pearl Harbor and 9/11, the sense of outrage and violation must have been the same. My mother was in her 20s during WWII, and she never forgave the Japanese or the Germans (even though they had nothing to do with Pearl Harbor); not even the Germans and Japanese born after the war ended.

Still, this is a new world. As far as I can tell, there has not been a formal declaration of war anywhere on earth since the USSR declared war on Japan in 1945.