I'm sorry but I have to say I believe that gangs are the #1 threat to America not right wing nut jobs but they don't help either.
The best way to undermine the power of gangs is to legalize drugs such as marijuana. Take away their money base and instead of spending billions fighting drug use, tax it and make billions on the sale to deal with the people who get abused by it. Haven't we learned anything from the lessons of prohibition? During the prohibition era gangs (call them mafia or whatever you want) controlled the sale of the liquor and made money off of it. They were violent and threatened the normal citizens. Once alcohol was legalized again the gangs lost a lot of their power. They had to move to new areas of revenue (gambling for instance) where there were more prohibitions against what people wanted. With legalized gambling another source of revenue has been taken from them making them move to drugs.
If we want to stop the gangs stop making things illegal and regulate and tax them instead. If you want to reduce human trafficking, legalize prostitution and make the girls register, get tested and pay taxes. It's kind of hard for someone to have a slave type of relationship with a woman if she has to walk into a government building to register. If you want to defund the gangs take away their income sources and stop spending money trying to fight the drugs. Legalize them, tax them and make money for social programs to help the addicts. That way the gangs lose their power.
I know this thought process will upset the moralists who want to impose their view of morality on others but forcing your views of morality on others allows gangs to gain power and increases violence in the streets.