I think the culture of America is more responsible for gun violence than the greater number of gun owners. IMO it's like the argument that if you own a gun you are X% more likely to get shot with it. That mostly goes for gun owners that are not properly trained and/or do not take the responsibility of ownership seriously enough. Sure, some un-preventable accidents happen but by majority they were probably preventable.

Also, I have a feeling that there are just more REGISTERED gun owners in America than in a lot of other countries, but that is just my flash intuition. It could possibly be an error of statistical analysis that Americans own more guns and are more violent. Can you link to the stats that you mentioned or list the search query that you used, by chance?