The USA won't do much about gun violence because "Americans" fantasize about heroism.
They fantasize about a situation where they can be heroic...
They fantasize about a situation where something happens, and they can be the hero with a gun to stop it.
It's this fantasy where the quote "only a good guy(me) with a gun, can stop a bad guy with a gun" hails from...
But they forget one thing...a crucial little thing.

"Everyone is a good guy, until they aren't"

And as (mass)shootings have shown...