I say in a society which is a "gun culture" society, the US should have mandatory training in order to carry or own firearms. I don't mean a 1 day course but real training where people are put into a "jungle lane." This training needs to be not a just one time thing, it needs to be at least annual. There also needs to be controls put into place to protect the innocent from getting hold of a weapon in the home/car/purse, etc.
Placing a person and a weapon into situations where that weapon can potentially kill another requires robust training. As a former soldier, whenever we were training to go into harm's way, our training was robust and repetitive to gain muscle and mental memory.
It seems Joe or Jane Public can get a weapon in many states pretty easily.