Have you been asleep for the last 20 years. America has a VAST number of mentally unstable people, and the country has a vast number of guns. Combine those two factors and you get mass shootings about once a week, and it is probably more frequent than that. A mass shooting used to be almost unheard of; now, they couldn't be more common. The New York Times recently ran a list of the mass shootings in America over the last three years or so--I forget what number of casualties the paper used as a threshold--but there were SCORES of them.
Eventually, I hope, America will come to its senses and greatly reduce the number of guns in this country--if not ban most guns altogether. But conservatives--led around by the nose by the NRA and other pro-gun groups--are nothing if not willfully stupid--or indifferent--about problems in America: When reality conflicts with their opinion or their ideology, they are happy to ignore reality. Much easier to give us their silly "send prayers" BS rather than do anything to solve the problem. Same with pollution, same with wages and income, same with climate change, etc.
There is very little that can be done to improve the mental health of Americans, given the number of people without health insurance, given the crappy policies that do not cover mental health treatments, given the number of people who go through life with mental issues that are not diagnosed. But we could do something about guns.