US homicide rate: 6.5, Black population: 12.1%, homicide rate/Black %: 0.54

UK homicide rate: 1.1, Black population: 3.15%, homicide rate/Black %: 0.35 (0.65x that of the US)

So gun control seems to have helped, but not as much as 1500 vs 50,000. It would be interesting to see the homicide rate for UK Blacks specifically, but I could only find data about homicide victims by race, not perpetrators. Sources:

https://en.wikipedia.org/wiki/List_of_countries_by_intention...

https://en.wikipedia.org/wiki/Demography_of_the_United_Kingd...

https://en.wikipedia.org/wiki/Demographics_of_the_United_Sta...