Answer: I think guns play a significant role in American culture relative to some other cultures. There are definitely places, and groups in the US, who are more involved with guns than others. In terms of guns and violence, meaning people against people violence, to me this is something happening in very particular places, and for particular reasons. In areas where poverty and race issues play a big part, which I would say is in inner cities and in/close to the Deep South, there's more of a gun culture that extends to 'self protection.' I haven't looked at the statistics recentyly, but if I had to guess, I'd say that most gun deaths outside these areas are accidents. Crime is a result of corruption and/or poverty.
When you say "perceiving onself under attack/against all odds" I think of Florida's new Stand-Your-Ground law. The idea that people have the right to defend themselves is one of the cornerstones of American culture. In a country where it's legal to bear firearms, but where the consequences of shooting someone can extend to life imprisonment and the death penalty, some clear lines have to be drawn around what's legal and what isn't. I remember hearing it repeated over and over while I was growing up that if you shot someone in self-defense, you wouldn't get arrested. I do think 'This is mine" is one of the things that defines America as a culture. It forms the basis of the mindset about many things, from self-defense laws to attitudes toward welfare.
Just remember there are almost 320,000,000 people in the US. And many of them are on the Internet. The vocal ones giving you that impression aren't necessarily the majority.
So yes, and no. I think there's probably some overlap, but most people who exhibit the "this is mine" or "everyone's against me" mindset are probably not murderers. You can tell that's true because there are more guns than people in America and some of us, most of us, have never been shot.
@shun_geki_satsu asks: i was actually thinking of "socialism–us," "terrosism–us," or how at sports, no matter how accomplished an US team is,…theres always the narrative of the uphill struggle of the underdog, the heroic, patriotic, whatever. victim of tweet length
Answer: I think of this as more a problem of isolation. This HUGE, geographically, country surrounded by oceans. Unlike Europeans, most Americans never leave home. Which is not to say they don't travel, but there are (by my very rough calculations) six million square miles of America to explore. So I think many Americans have a harder time forming realistic pictures of other countries.
We are, in a way, the perfect group for believing that everyone is against us. It's instilled in us from birth. Socialism v US has been beaten into us. I know older people who will still shout contemptuously that something is SOCIALISM, like it's the worst thing in the world. (And I've heard a few younger people do this, too, though I found it more shocking.) Give my coutrymen a buzzword that they can unite against, and you'll have an unstoppable, albeit ignorant, force.