White men are still a large demographic between the ages of 18-100 so the per capita rate is not that high or out of proportion. A child can’t exactly commit a mass murder and are disproportionately minority relative to older people being disproportionately white. Adult men are the main perps of violence.
European Murder Rates Compared to the United States
http://gunwatch.blogspot.com/2013/01/european-murder-rates-compared-to.html
If you look at non-hispanic whites, the murder rates are the same as for Europe.