American's have the right to have them, guns are a large part of American history. The government will never take away guns, millions of people have them (and millions of people don't use them to harm others). On that note, guns don't kill people, maniacs do. You'd have to take away blades, bats, and your hands and feet to prevent people from killing others, and even then psychos would find a way.
What's the murder rate in the US compared to the UK? I think those figures would be interesting.