It would hit them financially, but they would more than likely overload the US with cocaine, meth, and heroin to make up for it. It isn't going to get rid of them, or lessen the violence at all.
I really doubt that they could make up their lost profits through coke, meth, and heroin. The demand simply isn't there to make up for it all.
As for getting rid of them, of course not. In order to stand a serious chance of doing that we would need to legalize all drugs. (something I support) As for the violence, maybe, maybe not. It would deplete their financial resources, which would weaken their position vis a vis the government.