I think the #1 reason for violence in the US is directly because of the lucrative drug market. WHY WHY WHY can't the government just legalize drugs and regulate everything already? Doing so would raise huge sums of money that they desperately need, and cut the head off the whole problem for violence in the first place - gang warfare.
Gang or drug dealer violence is a relatively small percent of US violence. The majority of homicides are between "friends" and family members.
As for legalization, it wasn't really that many years ago when only like 20% of the US public favored it for marijuana, forget about hard drugs. Now for pot it is around 50%, but it is still the older people who do most of the voting.
And yes, the prison system is huge and probably does things to try to make the public afraid of legalization. And :
[ame=http://www.youtube.com/watch?v=lyLJtkxPC6I&]The CIA and Crack Cocaine - YouTube[/ame]
[ame=http://www.youtube.com/watch?v=l6VYd1gpiNk]CIA Corruption - CIA Drug Trafficking - YouTube[/ame]