There is a monumental difference between correlation and causation. I would like to see a proper multivariate analysis to see what are the independent risk factors in different countries. I'm betting that loads-a-guns plays a greater determinant on the odds ratio. As has been so oft stated, getting angry with one's fists or a knife makes killing people a lot harder than with a gun.

There is also the fact that there are groups disenfranchised in Europe.

America has free borders between states. Local restrictions would only mean something if there were regular stop and searches with confiscation of weaponry with a large fine.

I'm still not seeing facts. I prefer peer reviewed research.