I'm not sure how American cars are more violent that any others. If anything, America has been a leader when it comes to making cars that are both safe and friendly to the environment. Maybe they're a little more extreme than what your typical European drives, but both Europe and Japan have shown that they can build cars that are just as extreme, if not more so, as anything to come out of Detroit.
And as this show in Belgium shows, even with all their culture and sophistication, some Europeans are interested in American iron too.