I think the mention of games and movies is an example of the culture, not necessarily the cause. America has been historically more violent than other 'civilized' nations. In 1900, I don't think there were a full dozen shooting deaths in London - at a time when there was no gun control. In America, on the other hand, a lot more shooting was going on (I think John Lott had stats on this). Maybe it's due to our mishmash of cultures all tossed together in one country. But it doesn't seem to be racist in nature - as crimes seem to happen in their own cultural enclaves, primarily. Blacks shoot blacks, whites shoot whites. Maybe these enclaves somehow foster violence - due to poverty or some such. I've got no idea.
American fiction, for example, tends to be a tad more violent than British. Example: (Britisher) G.A. Henty wrote around a hundred historical fiction pieces, usually involving a war (typically something in the British Empire). His heroes typically become officers, and the battle scenes are simply a story of tactics and (especially) leadership. The hero keeps a cool head and keeps his focus on the mission, which is not usually shooting everybody. Compare this to the Hardy Boys. You are almost guaranteed a knock-down, drag-out fistfight at some time, usually more than one. If Henty has one, it's generally a fight with Marquis of Queensbury rules - fencing match, boxing match. The Hardy's just go in and try to beat everybody up, no rules allowed.
