I'd agree that the main factors in determining the rates of gun violence in a society are likely to be cultural rather than merely access to guns. There are places with high levels of gun ownership and low rates of gun crime (though I don't think the reverse holds true).

However my understanding is that those are generally predominantly rural societies - what is odd about the USA is an urban society which has somehow built into its culture a reverence towards gun ownership.

The propensity towards violence arises primarily, I suggest, from other aspects of urban life, such as overcrowding and erosion of informal communal controls. Where guns are present, this feeds back into this, so that incidents which would normally involve relatively less lethal actual or symbolic violence (fists, boots, even knives, for that matter, at one extreme, or just verbal abuse at the other) turn lethal. The presence of a gun means that it is very easy indeed for a momentary loss of self-control to cause one or more deaths.