Gun violence in the U.S. is a hobby interest of mine as a researcher. Skimming the discussion here, there are several things it would be good to keep in mind:
0) Gun murders in the U.S. are a very low percentage of deaths (0.39%) and preventable deaths (~1.1%, there's some disagreement about what's "preventable"). That's 0.0036% of the population per year gun-murdered. That this statistic is 3x some other country's is irrelevant because 3x a small number is still a small number. If your goal is to prevent untimely deaths, focus on boring things like falls, car accidents, and diabetes.
1) "Mass" shootings are a tiny fraction of all shootings. In the U.S., by firearm murders, it's about 3.5%. And that's using an extremely permissive definition of "mass shooting". Usually 3+ or 4+ people shot, not dead. When most people think about a mass shooting, a gangland shootout doesn't come to mind. The people coming up with these numbers do this on purpose ("advocacy numbers"), and you should be on guard. The distribution over # shot or # dead is telling.
2) Your kids are really safe, and worrying about a child getting shot, training for it, etc. does much more harm than good. We've managed to get child mortality from all causes to be very, very low. Worry about whether your kid is happy, has friends, is fat, has good mentors. This is pretty much exactly like "stranger danger" from the 1980s in the U.S. in a statistical sense, and I would say that contributed to the current regrettable situation where kids aren't allowed to roam free at all.
3) Stuff like the recent mass shootings in Buffalo and Texas makes it in to your minds because it's profitable for news media. Not because it's something you should actually think about or worry about, not because it's a real threat to you or anyone you know, but because it sells advertisements. Real risks to you as an adult reading this in the U.S.A. are traffic accidents, falls, and being too fat.
4) Ppl be like "We banned guns in Scotland and we haven't had a mass shooting since!". Great, but it's like saying I can't drown if I don't get in to the pool. Mostly true, but missing the point. The real number we're concerned with here is premature deaths, or perhaps an overall murder rate. Banning guns might result in a lower murder rate, but there's going to be some substitution (e.g. knives for guns, Glasgow being the "stab capital of Europe"...). Scotland is a very fat, very drunk country. Much more good would have been done for public health by banning Irn Bru and alcohol, but you haven't chosen to do that because people find them rewarding. People find owning guns rewarding too, it's just that the costs end up on the front page of the newspaper (mass shooting) rather than ignored because they're so quotidian (millions of years of life lost due to being comically unhealthy).
5) Don't focus on the type of gun. The fact that AR-15s are used in a lot of "mass" shootings reflects the fact that they're the Toyota Camry of guns. Good value for money, reliable, etc. If you saw a lot of a specific kind of traffic accident, and Toyota Camrys were frequently involved, would you start to scream "Ban the Camrys!"? It doesn't make any sense. The vast majority of gun murders in the U.S. are committed with cheap pistols. <2% are committed with "long arms" of any kind, including AR-15s.