Yet if you look at a more granular level we see that theory fall apart. Look at the crime stats for Media PA and then for Chester PA. They're 7 miles apart, have the same gun laws, yet there are wildly different outcomes. Socioeconomic factors seem to be the most correlated (some studies and books support this). Gun ownership is realtively high in Switzerland and Canada (including illegal guns from the US) as well, yet we don't see the issues there on the levels we would expect - the correlation doesn't track. Plus, we should be looking at reducing all violence and crime, so addressing the socioeconomic factors is the holistic approach that would provide the most benefit to society. Also, re: mental illness monopoly - most other ODEC countries have much better access to healthcare, including mental health services. If you look at the mental health scores by country the US falls near the bottom.
Another interesting thing is the focus on guns and gun laws that don't match the events. The gun laws being proposed would do almost nothing to prevent the events the media swarms to (Rand analysis shows). Most of them would have little impact on crime in general. The main way places like the UK get to low levels of gun violence is by near prohibition on ownership over generations. Then we will see that violent crime is still twice the US level, even after adjusting for differences in definitions.
I don't necessarily disagree with your conclusion but comparing gun/crime numbers to Canada isn't particularly helpful. Canada has wildly different tolerances of what is legal as far as violence goes, not to mention the suspect nature of crime statistics in the US when comparing areas with differing socioeconomic status. Many in the US see it as perfectly reasonable to use deadly force to defend property, as that's been heavily pushed into legislation (ALEC's 'stand your ground' gun laws) See this article about self-defense in Canada: https://www.cbc.ca/news/canada/self-defence-what-s-acceptabl...
Your last line is vague - can you expand? The UK has far, far lower murder rates than the US so do you mean that the UK has twice the amount of non-murder violent crime?
"use deadly force to defend property, as that's been heavily pushed into legislation (ALEC's 'stand your ground' gun laws)"
Stand you ground laws do not allow for deadly force to defend property. Ones life must be imminent threat of death or great bodily harm (or kidnapping, or rape, or any of the above in defense of a third person). The vast majority of places do not allow deadly force to defend property. I believe Texas has a law that sort of allows it on the presumption that anyone committing a felony on your property at night has deadly intent). But that's an exception. Reasonable force still applies as well.
Another interesting thing is the focus on guns and gun laws that don't match the events. The gun laws being proposed would do almost nothing to prevent the events the media swarms to (Rand analysis shows). Most of them would have little impact on crime in general. The main way places like the UK get to low levels of gun violence is by near prohibition on ownership over generations. Then we will see that violent crime is still twice the US level, even after adjusting for differences in definitions.