The Americans have always been using guns, and it’s been legal since 1791, where the second amendment was formed.
In Denmark, not everyone can own a gun. You can get a hunting license at 16 years old and you must pass a written and practical test to have a long gun.
The gun has to be stored in an approved and locked in a gun safe. You must be 20 years old and be an active member in a shooting club for 2 years to buy a handgun.