The Prevalence of Mental Illness in America
Mental illness is often used as a red herring for gun control. Mental health is extremely important and worthy of increased funding and attention, but it shouldn't be conflated with lax gun regulations.
Gun ownership in America
Just 3% of American adults own 50% of all guns.
It's currently against the law for the government to have a searchable database of gun ownership.
Summary - https://www.vice.com/amp/en_us/article/wdbd9y/the-atfs-nonsensical-non-searchable-gun-databases-explained-392
NY Times - http://www.nytimes.com/2012/12/26/us/legislative-handcuffs-limit-atfs-ability-to-fight-gun-crime.html
Wikipedia - https://en.wikipedia.org/wiki/Firearm_Owners_Protection_Act
The CDC (Centers for Disease Control) is forbidden from researching guns as a cause of injury and death by the Dickey Amendment:
Wikipedia - https://en.wikipedia.org/wiki/Dickey_Amendment_(1996)
Mass Shootings -
Opposition POV -