The trouble with trying to solve "the violence problem" in the US is that if we magically removed all the violence from the country -- performed a "violence-ectomy," -- there wouldn't be much country left.
This is sort of like when the Big Texan lay dying in the hospital, and the local undertaker despaired of finding a coffin he'd fit into. So the doctor gave the Big Texan an enema and the next day they buried him in a shoebox.
The US today is a mentally ill society, populated in part by semi-educated men and boys with cowboy mentalities who carry guns, are afflicted with violent tendencies incurred by the habit of war and a militarized culture, and have a penchant for violent solutions as the answer to all one's problems. It's expressed culturally in the popularity of fictional characters like Mr. "T," a bully who threatens even his friends with violence, and is considered "cute." Or in stories such as Clint Eastwood's movie, "The Unforgiven," in which a bottle of 90-proof whiskey serves the same function as Popeye's can of spinach, and is the necessary, magical prelude to either a mass shooting or a memorable ass-kicking. And I could go on and on and on...
We've got the violence against women law, violence against children laws, violence against pets laws, yet we're still the most violent society in the history of the world, leaving the Mongols, Huns, and Romans in the shade. Even our "easy motoring" way of life is violent, and consists of assaults on the health and viability of the earth herself -- our own mother! Do we really want to be in the company of matricidal monsters like Nero?
So to answer the question on everyone's mind, the law should be that no American adult can buy a firearm without first submitting to a comprehensive mental examination by a panel of psychiatrists who have themselves been certified free of paranoia, delusions of grandeur or other manifestations of hallucinatory thinking, and upon a finding of sound mental health and a non-delusional outlook, be permitted to buy one (1) firearm and 20 rounds of ammunition at a time.
That should make a dent in it, anyway.