For comparisons to be realistic I think it is fair that we only include first world nations and measure by how many murders per 100,000 people.
Russia is no.1, Estonia 2, US 3, Latvia 4, Finland 5, Canada 6, Czech Republic 7, New Zealand 8, UK 9, Australia 10.
The USA's murder rate is almost 5x Australia's. Why is this?
Why is the UK's murder rate higher than Japan? Germany? Spain? Austria? You guys must be some pretty crazy psychos over there.
There is an assortment of reasons why some countries have higher murder rates than other, one being that America has 4 times as many people than the UK, literally we can stack every person in the UK 4 times here, you are bound to have 4 times as many crazy people that are willing to murder.
If we didn't have guns here, people would be killing with other objects (they do already). Guns are a tool, the same way we used to use clubs and rocks to murder, it's an object, the human mind is what murders.