That's why I said "first world." Yeah, we don't have as many gun-related homicides as many third world countries, but we're part of the first world, we should have much higher standards.
We have higher violence in general than most of the First World. Banning guns wouldn't change that. You have to address the root causes of violence to reduce it. Mental health issues are one of those root causes.
Access to guns can't really be considered a root cause, because the vast majority of gun owners don't commit acts of violence. All you can really apply is psychological background checks to keep guns away from unstable people.