Ok I'll Bite. How about income inequality and a history of racism coupled with a militaristic national chauvinism and its close cousin intolerant idealism.
[WS:] The US is hardly unique in these characteristics, other countries (e.g. Germany or Japan to name the most obvious) have even worse track record - yet significantly lower homicide rates. So it's not working. Try again.
BTW, AFAIR from my previous life as a TA for a criminology prof at Rutgers, the social cohesion argument that crime is caused by a breakdown in social cohesion and individual stakes in the community (which I previously outlined) advanced by the Chicago School studies, Travis Hirshi & Co. is the one that has received the most empirical support.
The social inequality argument is basically a politically motivated opinion without much empirical support. It does not even make much sense when you think about: most poor people who should be criminals according to this theory - in fact are not. Moreover, many rich people who should not be criminals according to the same theory - in fact are.
Wojtek