"The U.S. is a very large country ... larger than Europe .... may regions in the U.S. have a murder rate equal to GB on the other hand many parts of Europe"

The US population (about 300 million) is less than half that of Europe (780 million). Europe is a little larger than The USA even if you count largely unpopulated Alaska.

If there is a region in the US of comparable population to Great Britain with less than twice the murder rate, I don't know what it is.

I think that among G20 countries the US has the most murders apart from Russia. It has a higher murder rate than every European country but Russia and Asia.

http://en.wikipedia.org/wiki/List_of_countries_by_intentional_homicide_rate