I'm sorry to ask, because I know you're going to say something stupid... but by who? Who, exactly, debunked that the EU has less violence than America? Because I'll tell you who a liar is, that guy.
And no, video games aren't the source of all violence. Look at the old west, back when Billy the Kid, Nathan Bedford Forrest, Jesse James were all wandering about. And what did all of those people do for a living? Kill (or form the Klan, in Forrest's case). Video games don't create violence, people are naturally violent. I know, I know, it's hard to accept that after sitting down with your pastor to read about the rape of Jericho or the enslavement of the Philistines, but it's true!