It can be hard to compare apples to oranges

"Legal historian Richard Maxwell Brown has argued that Americans have more homicides because English law insists an individual should retreat when attacked, whereas Americans believe they have the right to stand their ground and kill in self-defense. Americans do have more latitude to protect themselves, in keeping with traditional common law standards, but that would have had less significance before England’s more restrictive policy was established in 1967."
http://www.wmsa.net/pubs/reason/reason_nov02_crime_in_uk.htm

"The failure of this general disarmament to stem, or even slow, armed and violent crime could not be more blatant. According to a recent UN study, England and Wales have the highest crime rate and worst record for "very serious" offences of the 18 industrial countries surveyed."

But despite, or because, of this, violent crime in America has been plummeting for 10 consecutive years, even as British violence has been rising. By 1995 English rates of violent crime were already far higher than America's for every major violent crime except murder and rape.
http://news.bbc.co.uk/1/hi/uk_politics/2656875.stm