WW2 can actually be seen as a continuation of WWI. The conditions after the first war, (i.e. the Treaty of Versailles) greatly contributed to Hitlers rise to power. I don't think 9-11 is the same as Hiroshima and Nagasaki, though. We were already at war, and an invasion of Japan would have been a bloodbath. The A-bomd could conceivably be seen as the lesser of two evils. 9-11 was just evil.
