One night of firebombing in Dresden killed over 150,000 people. But that was a "real" war and not a terrorist attack.
I do not believe there has been a terrorist strike of this magnatude anywhere else. "Just" lots and lots and lots of smaller events that "only" killed a few hundred people or less at a time.
Europeans are more used to terror attacks and we do not let this stop us from going about our normal lives. Like anything else the more it happens the more it just seems "normal".
I just hope that the Americans never have to get used to this, as be it one or ten thousand killed, it is all a stupid waste of life.
Stewart.