I'm not sure I'd lump Hiroshima, Nagasaki, Dresden, and Tokyo in with "terrorism," but one thing that occasionally surprises me it how little people in America know of the Baader-Meinhof Group/Red Army Faction of Germany in the 70s and 80s.
It is so little known than a common phenomenon called the "Baader-Meinhof Phenomenon", where you hear about some obscure item or "thing" and then later that day your hear about it again in a totally different context. For most Americans, the Baader-Meinhof Group is so obscure that they literally ended up as the namesake for a phenomenon that is all about obscurity!
But that said, consider these things about this group:
-- Their impact on Germany has often been described as comparable to the impact of 9/11 in the United States.
-- One of the namesakes of the group, Ulrike Meinhof, was a very famous journalist before helping break Andreas Baader from police custody and becoming a terrorist (a modern American equivalent might be Rachel Maddow, or Diane Sawyer one day deciding to join Al Queda).
-- Imagine a group today deciding to kidnap and/or murder the John Roberts, the head of the surpreme court, Eric Holder, the Attorney General, Tim Cook, the head of Apple Computer, and Jamie Diamon, the head of Chase Bank. The equivalent of these people were all kidnapped and/or murdered by the Baader-Meinhof Group/RAF.
-- The German state used the threat of this group to dramatically bolster their federal police force, increase the use of computer-aided detective work, institute far reaching "anti-terrorism laws" that in retrospect had very little to do with stopping terrorism, and more.
-- At one point a German survey was conducted that shows that more than 10 percent of the population supported this group to the point that they would either willingly help them or would consider it. (about 8 million germans out of 6 million).
The intro chapter to my forthcoming book about the group you can get a good overview of them and why they were important: