In general one usually gets more meaningful results when a) comparing geographically and/or culturally similar countries for things like these. E.G the UK has half the mortality rate of the US, Canada and the EU have 2/3 of the US rate. And b) compare trends, not single values. E.G. US rates are rising (which I as a layman would interpret as speaking against the firearms thesis), while the rates of Lithuana and Japan are falling.
In general one usually gets more meaningful results when a) comparing geographically and/or culturally similar countries for things like these. E.G the UK has half the mortality rate of the US, Canada and the EU have 2/3 of the US rate. And b) compare trends, not single values. E.G. US rates are rising (which I as a layman would interpret as speaking against the firearms thesis), while the rates of Lithuana and Japan are falling.