I believe GP's claim is factually accurate. The USA has the 4th highest homicide rate in the OECD, after Mexico, Turkey, and Estonia [1]. Roughly 2/3 of US homicides are using firearms [2]. After reducing the US homicide rate by a factor of 3, the US would still be 13th (out of 34) on the OECD list, between Portugal and France.

[1] http://www.businessinsider.com/oecd-homicide-rates-chart-201... [2] https://en.m.wikipedia.org/wiki/Gun_violence_in_the_United_S...