The reliability of underlying national murder rate data may vary.
Homicide rates may be under-reported for political reasons.
Homicides are also a fraction of violent crime, let alone all crime.Also, SK suicide rate is like 70% higher than US, and 50x their homicide rate; as a collectivist culture, it's not unthinkable to suspect that some of the people who would have been murdered in other countries are just shamed into taking themselves out instead.
And, FWIW, SK's 25+0.5 per 100k suicide/homicide rate eclipses America's 15+5 (roughly). If you don't want to die a violent death at the hands of a human being, the US is safer than SK.