Hmmm, some interesting questions are raised here. When living in a country/society that still carries many physical, if not psychological, scars 60+ years after the last war ended, one often tries to put things in perspective.
Imagine that on 9/11, six hours after the assault on the twin towers and the Pentagon, terrorists had carried out a second wave of attacks on the United States, taking an additional 3,000 lives. Imagine that six hours after that, there had been yet another wave. Now imagine that the attacks had continued, every six hours, for another four years, until nearly 20 million Americans were dead. This is roughly what the Soviet Union suffered during World War II, and contemplating these numbers may help put in perspective what the United States has so far experienced during the war against terrorism.