> no-one would seriously advocate taking away all guns
While I believe this to be true, virtually any sort of "turn in some of your guns" event in the USA would... not be viewed with any nuance at all. Even machine guns were more-or-less exempt from turn-in, provided they were registered by a certain time. Moreover there are already very, very many semi-automatic pistols, revolvers, rifles, and shotguns in circulation--it's not as if a lot of folks have a bolt-action 22 cal rifle and just a few have semi-automatics--the sort of guns that can be fired and reloaded somewhat rapidly, that's what we've got. Setting aside the fact that a rifle is more powerful and aim-able, but harder to conceal, compared to a pistol, I'm not sure what characteristic of a "bad" gun the American government could successfully put forth.
All that said--from whom would you propose to confiscate what guns?
> Another issue is with your stated statistic of death via mass shooting. This obviously ignores maimings and other non-deaths, and also deaths from guns in non-mass events, such as burglaries, accidents.
Well, agreed! Mass shootings and terror attacks inflict many fewer casualties on the American population compared to robberies, gang and drug violence, alcohol and smoking, fatty foods, traffic accidents and DUI, swimming pools, etc. However, it does not seem to me that these other perils are used to buttress the case for banning the instruments of such trouble. I don't mean to be glib, and indeed it is hard to imagine a bad actor using an undoctored swimming pool against innocents, but it does seem to be the case that the electorate lacks the will to stamp out certain risks. And this lack of will is not really related to the measurable impact of the problem.
> What happens to a young child's mind from having to participate in active shooter drills?
We could reflect on the schoolhouse duck-and-cover drills for nuclear war in the 1950s and 1960s--like, isn't contemplating nuclear annihilation and nuclear winter much more terrifying and existentially dreadful than locking the classroom door? Maybe it isn't a good idea to traumatize children with visions of a terrible but statistically very remote fate. On the other hand, local police and school districts must be seen to be doing something, so maybe it is practically unavoidable.