Your lack of understanding the American gun culture is not a surprise. Many Americans also fall victim to our fake media and faked studies. The hard truth is the murder rate in the US is lower than many realize and firearm deaths are not at the top of how these deaths occur. Even cities like Chicago that stay at the top of our violent weekly murder statistics is actually a very safe city except for a few small circles of gang-controlled properties. Violence especially violence involving firearms outside of those areas are rare. We also have a very different gun culture between our major cities and outside of them. The USA is massive; in the time it takes to drive across England you cannot drive across most of our states. Texas alone takes two days to cover, and it is our second largest. Depending on where you live outside of our cities you can encounter bears, wolves, moose, snakes, large cats and a lot more dangerous animals, much more likely in injury you than an armed human. I carry every day, there are creatures on my property than can hurt me, my children or my livestock.
American's own weapons for recreational shooting, competition, collector value, self-defense and dozens of other reasons, not trusting our government and waiting for an invasion are not really high on our list. From antelope to prairie dogs, we have shooters making long range shots they consider easy from coast to coast. My father and I shot rifles every Saturday from about age eight until I joined the service, by the time I joined I had easily shot 80K or more rounds. A brick of 22 caliber each, weekly for 10 plus years, not counting all the others we used to hunt, plink and just hit cans with. If I could see it, I could hit it if it was in range and yet none of us ever considered shooting humans. Granted not everyone grew up like I did. There was a clear line between rural, and city raised trainees. We taught them as much about how to shoot as our military instructors.
You mentioned active shooters, that is another issue that tends to be misunderstood. Most of the last ones were gender confused teens on mind altering drugs. Also, almost all active shooters are taken out by someone armed in the targeted group. It is actually a rarity for armed officers to take out an active shooter, more so if it takes place outside of a major city. As I have mentioned most Americans will never be anywhere near a murder scene, active shooter or other.