Which way does the causation run, for both?
https://ourworldindata.org/uploads/2013/03/homicide-rates-in...
During the 20th century the US homicide rate fluctuated from 5-10 per 100,000. In Germany, France, Sweden, and England, it was below 2.5 the entire century.
Focus on France and the UK (since Germany and Italy were unstable states during part of that time). In France, the first gun laws date to 1938. By that time, France’s homicide rate was about 1 per 100k, about what it is today. The first UK gun laws started in 1920. The UK murder rate has gone up since that time. (Handguns, which are responsible for most US gun homicides, weren’t banned in England until 1997.)
How did gun control cause low homicide rates in those countries when homicide rates were already very low (at current levels or even lower) before gun control? That’s an “umbrellas cause rain” argument.
Likewise, the death penalty wasn’t eliminated in the UK until the 1950s. Criminal justice reform in Europe generally happened in the 1960s and 1970s.
How did criminal justice reform cause European homicide rates to be lower when they were already very low?
The idea that gun control and lenient criminal laws caused lower homicide rates in Europe contradicts all the available data. The only supportable conclusion is the opposite: that Americans remain resistant to lenient criminal justice laws or disarmament because America is a much more violent society.