This morning I also replied to this, but it seems that I did not clicked on submit.
You have a lot of valid points Mark, but you know that we can put figures as we like and how they best fit us.
I knew about the Second Amendment in your Constitution, which surely comes from your history and your large country with many places almost inhabited.
There is also something more: The USA is the major producer of firearms!
About your point 4, yes, they do NOT obey the law and can get guns easily, but take for ex the Newtown School Shooting, could it have been avoided, if the gunman wouldn't have had access to a gun? And so many other mass shootings. No gun should be available to depressed or inestable people