Easy access to a surplus of guns is one component of the problem, but we need to ask ourselves whether or not there's something in American culture or lifestyle that drives people to keep doing this. "Unintended" media glorification of the shooter is certainly part of the problem, but maybe not all of it.
Pretty good data here. You can see that the proportions of the number of guns per capita between countries does not scale to the number of firearm homicides (Norway, damn!). Also, the overall homicide rate is dropping, so that's good. I wasn't aware that the legislation to prevent the sale of automatic weapons and expand background checks was defeated in Congress. Thanks, NRA.