Whatever drives violent crime in the U.S. does not seem to be the presence or absence of guns.

The white murder rate in America is about the same as it is in Europe/Canada, etc. The black murder rate is about the same as it is in parts of Africa. (Something like 10x the white rate.)

First look here to get a rough idea of the murder rate in different parts of the globe:

http://en.wikipedia.org/wiki/List_of_countries_by_intentiona...

Take a look here for the murder rate in different American states:

http://www.deathpenaltyinfo.org/murder-rates-nationally-and-...

Notice how this is a very similar list:

http://en.wikipedia.org/wiki/List_of_U.S._states_by_African-...

With some corrections for urbanization, the correlation is even more extreme.

Also see the discussion and figures here: http://www.lagriffedulion.f2s.com/hispanic.htm