If you've read Colin Woodard's "American Nations", you might be aware that there are strong regional cultural differences in the US. Some have a stronger propensity to violence than others, most notably the ones where the original colony had a popular bloodsport (e.g. the "gander pull") differ from the ones there that colony had stick and ball sports. For the folkways of the original colonies, check David Hackett Fisher's "Albion's Seed". Woodard's work shows that a lot of the differences in culture have carried on into current day. He's here on Medium, BTW. US gun deaths by state here.

Those states with a bloodsport heritage have outsize per-capita representation in both the Electoral College and the Senate. Our constitution is written so as to make it difficult to make changes, so even a minority can block things - and putting restrictions on gun ownership is very much a change. On top of that, "gun rights" has been pushed by organizations like the NRA (really a gun manufacturers' organization) to the point that even making changes that many gun owners agree to (e.g. background checks, safety training) are considered to be a "slippery slope". Major reason I left the NRA in the 80s. (I'd been a member as I was a handgun competitor so I needed a membership same way I needed an AMA membership to race motorcycles.)

This is a very long-winded way of saying yes people are angry, but it’s not just a matter of how many people get angry but where those angry people are and whether they vote.

Off topic: I've seen at least one study (on PubMed) that there's a connection between a country's latitude and the suicide rate. I'd guess it's seasonal affective disorder...