I lived in Germany for about 19 yrs. I can tell you that in a lot of European countries not all violent crime is reported (at least in the news). I don’t know if that would effect the tallies of murder rates for countries but it would not surprise me if it did.
I have also lived in Europe and am in fact married to a Swiss woman. I have seen first-hand, in Germany and France and Switzerland, how cities are transformed after dark to very dangerous places. I have seen this in Paris, where well-known tourist destinations become havens for all kinds of vice after dark. I have been in German train stations at night, when gangs ran wild with no police in sight. And even in genteel Switzerland the cities become dangerous after dark, and the police refuse to help. I have seen this first-hand. All very much different than in America. You have to experience it to believe it.