Guns aren't the problem. The American culture of violence and vigilante justice is. And of course the universal reasons to crime: inequality,[lack of] education, social mobility etc. (
http://www.epi.org/publication/usa-lags-peer-countries-mobility/)
The american dream is a dream in America, but a reality in Scandinavia and Australia.
It's easier and faster to ban and/or limit guns rather than change the mentality of millions and make the much needed social and economical reforms (GO BERNIE!). Although the value of the message that is not accepting guns and a violent society should not be underestimated.
The idea that armed civilians is a preventive measure against crime is beyond stupid.