Huh? We killed a lot more civilians in Europe during WWII, and there wasn't much backlash against that. At least not until Dresden, when everyone realized that the war was over and it was unkind to burn tens of thousands of people to death.
Well, I'll be the first to admit my dearth of knowledge on other wars, so I could be completely wrong. It just seems to me, a lot of Americans seem to think that all Arabic people are terrorists, so they don't care that much when they hear about civilian casualties. If we were currently at war with some European country, I highly doubt we would be as OK with civilian casualties.