What do you think that difference in homicide rates proves? It’s caused entirely by racial disparities in homicide victimization rate. The NYC homicide rate for white victims is about 9 per million: https://www.nyc.gov/assets/nypd/downloads/pdf/analysis_and_p... (7% of 343 homicides divided by 2.7 million). The homicide rate among white people in London was also about 9 per million: https://aoav.org.uk/2024/londons-2023-murders-examined-key-f... (43% of 103 homicides divided by 4.7 million).

It seems unlikely that this pattern of homicides would be explain by differences in general government policies between the U.S. and UK, such as healthcare policies.