Assault weapons make it far easier to kill more people and are heavily involved in mass shootings. Also while handguns are more prevalent overall they are also pretty goddamn easy to get even for those under 21 due to the gun show loophole. We also have a severe lack of red flag laws or laws similar to that in the country. Weird how our homicide rate via firearms are exponentially higher than other first world nations.
America's problem with mental healthcare has risen since the 90s. We have also seen a rise in firearms homicides and mass shootings since the 90s. We also have extremely expensive healthcare that can be very hard to get on a consistent basis or afford especially for those who really need it. The connection is pretty obvious
Oh so you're just ignorant. America has poor metal healthcare as well as expensive healthcare causing the average American to not be able to afford most health services. This creates a health care crisis which branches off into a mental health crisis. We also have extremely lax gun laws which allows mentally unwell people to easily access firearms. Sometimes these mentally unstable people commit mass shootings.