The way I see it, banning guns is like banning the drug trade. Look how well that's going for the US. America's citizens are so used to using guns and rifles, that banning rifles outright would just lead us to something like the War on Drugs we are already fighting. Instead of drugs, we'd be seeing rifles and handguns making their way to the streets. Not to mention the costs of maintaining this "War on Guns" would send our already fragile economy plunging.
To combat the homicide statistics: It's about upbringing. I've seen some terrible parents in the U.S. that don't care if their excuse for offspring drops out of school, becomes a dope addict, and violently kills his dealer for not being on time. If the parents do not teach their child how to deal with stress and anger, they're going to probably murder someone at some point in their life, whether its with a gun, knife, RPG, etc. On the other hand, some parents will discipline their child well when he hits another kid, and he will grow up to be successful in life.
I'm going to take a guess, and say that Britain's parents discipline their child more than some of the redneck/Homey-G parents* in the U.S.
*I'm not saying that all parents in the U.S. are rednecks or home-dawgs, because my parents, and many parents that I know are not like that. I'm using an example