There are large chunks of the US where a long gun is considered first as a tool, and considered as a murder weapon second, if at all. It's the way my father was raised, and his father before him, first on the Oklahoma plains and then in the undeveloped terrain along the Sacramento river in California, where his family hunted small game to supplement their meager income. Hunting season is a big thing in many midwestern states. In some areas you can go out on a November morning and hear rifle fire in the hills all around you, and it is absolutely normal. Young people are trained by their own parents to handle firearms responsibly well before any government entity is on the scene to run programs and gather paperwork.

Missouri has an early youth portion of their deer hunting season.

http://www.news-leader.com/story/sports/outdoors/2015/10/21/youth-early-hunting-opportunities/74262026/

Let that sink in a bit. This is really a different culture. And their possession and use of firearms does not move the needle on their murder rate one bit. Murder is almost entirely a big city problem, like it is everywhere else in the world.