Can you think of an example when prohibition has worked? I cannot. The gangs and criminals are armed with US weapons. Guns are traded for drugs, among other ways. I worked in two methadone clinics. Drugs need to be decriminalized with safe measured doses available. People can and do live their entire lives addicted. And I have helped people who chose to get off drugs.
Discussion
I don't disagree with a very legal and open drug policy, but that's not the problem. The problem is that on the Mexican side of the border, the criminal organizations are in power and no amount of legal competition in the drug trade is going to fix that without the Mexican government having the incentives to secure that area.
It is mostly impacting Americans and their streets, so Mexico looks the other way. It costs too much pain at home to fix. America should have declared these criminal armies a threat many many decades ago. Like other non-national threats, if the local government isn't going to do anything about it, America will just walk right in and do something about it.
Also, no one wants Fentanyl. It is used to dilute the real drugs. It's fake chinese drugs, like other fake chinese products. Why do we want these in America, even if you want legal drugs? We want American drugs, good ones, legal ones.