Like every country, the US has issues which contributes to violence, etc. To assert that US gun culture is not a significant factor in gun-related violence seems rather ignorant.
Not if you actually study the statistics. Legally owned guns aren't used in crime either in the US (with liberal gun laws) nor Sweden (with very strict gun laws), but if I, for example, correlate the number of firearms related deaths with the number of known (criminal) gang members, I easily get very close.
We're in a recent spat of shootings here in Sweden at the moment, and like the US it's all perpetrated by criminal gang members (the rest are an anomaly). It's just that we have fewer gang members...
So the deciding factor is how easy it is for criminals to acquire guns. (Far too easy with the EU's open borders is the answer in Sweden at the moment.)