*The real metric is whether or not firearm-related crimes are significantly redu...

The real metric is whether or not firearm-related crimes are significantly reduced in countries where there are prohibitions on firearms.

http://www.nationmaster.com/graph/cri_mur_wit_fir_percap-cri...

Contrast US with UK and Ireland.

Actually, I think US cultural exports are a large factor in the increase of gun crime in the UK and Ireland, a certain glorification of the weapon that gang members feel they need to live up to.