It might be just the way that American media portrays violence. I sometimes get the impression that Hollywood and others of similar ilk present violence as a "cool" thing in itself. That's not a recent phenomenon. It's been going on for decades. I haven't seen anything similar in other countries or cultures.
In the US media, good guys are often just as reckless and destructive as the bad guys. But I can't recall any major movies or TV shows in other countries which show the good guys using as much mindless violence as those featured in US media (except comedies or war movies).
There has to be a source for that. And I think that source is not one particular "thing", but a cumulation of factors over the course of American social development.
Although I admire America's pride in being "the land of the free", I think American people are generally prone to the "I'll do whatever the **** I want" type of attitude, moreso than people from other countries. If you combine such an attitude with all the social woes of today, plus alchohol and drugs, and finally, weapons (including firearms), the result doesn't look nice.
I also wonder about America's firearms culture. In the days of the colonies, firearms were undoubtedly essential for agriculture, self-defence, and defence of communities. But as law and order, and military organisation grew, firearms would have had less utility as essential tools. Perhaps over time, the firearm was turned from being a tool of defence and hunting, and more as a tool of leisure. Did this bring about a more blase attitude toward firearms and their usage? Although I agree with the principles behind the Second Amendment, I wonder if America was too free about firearms?
I bring up Switzerland again. It's a country with a staggering number of firearms. Many of those firearms are automatic rifles for military service, the type that even most avid American gun-nut wouldn't be able to own. Yet the rate of gun-related violence is very low there. Is it because the Swiss have a stronger sense of purpose about firearms and take them more seriously than Americans? After all, in Switzerland, dad's SIG550 is a tool for national defence, not a play-thing.