Yes, we have societal problems that contribute to this, but they aren't video games, Hollywood, rap music, etc. Literally every other western country has those same things, but not the same gun violence problem. We do have (1) easier access to firearms than most countries, and (2) a lot more of them spread throughout the country. Is that the sole cause? No. Is that a significant contributing factor? Absolutely. Is there a realistic way to dial the amount of guns back? Probably not. But restrictions on sales, including types of weapons, accessories, and waiting periods/background checks applied to all sales, not just storefront sales could help. Most gun violence in the US is with handguns, but the kinds of mass shootings that make the news are often committed with AR-15s and similar weapons. There is no doubt that high capacity magazines, the kind of accuracy you only get with a long gun, and rapid firing capability increase the lethality of firearms in mass shooting events.
Are there other awful societal factors, like the copycat effect? Yup. We see this with suicides: once someone does it, others do it. SFIrish works in communications for a transit agency. When there is publicity of someone commiting suicide by transit, studies show a significant uptick of more transit-related suicides. Would those people have commited suicide anyway? Maybe. But guns and trains are both rather final compared to other possible methods.
There also appears to be a uniquely American attachment to violence, and in particular gun violence, that is cultural, and comes from somewhere other than video games, Hollywood, etc. Perhaps its a copycat effect, writ large. The way of the gun, and all that. Not sure the cause, not sure how to address, but as BAB points out, there is a lot of fear out there about random violence that is really quite rare. Most shootings occur between people who have relationships with each other. I chuckle a little at the handgun for you and the shotgun for the spouse. Not saying this will happen to any of you, but my aunt nearly killed my uncle when they "heard something" that he immediately went to investigate, handgun in hand. Then she heard him, after having grabbed the shotgun, and blazed away. Fortunately, she missed. There was no intruder.
The fear of the random act of violence leads to a lot of people owning firearms, and a lot of people owning firearms leads to more access to firearms, and more access to firearms leads to more firearm-related violence. These are connected, but breaking that chain is a difficult task.
And most shootings are not "mental health" issues, in the sense of someone with a clinical mental health problem. There is a different between that (a clinical issue), and someone who snaps. That's why it makes sense to restrict firearms access for people with demonstrated anger management issues (domestic abusers, for instance).