“You want to know what this [war on drugs] was really all about? The Nixon campaign in 1968, and the Nixon White House after that, had two enemies: the antiwar left and black people. You understand what I’m saying?
We knew we couldn’t make it illegal to be either against the war or black, but by getting the public to associate the hippies with marijuana and blacks with heroin, and then criminalizing both heavily, we could disrupt those communities. We could arrest their leaders, raid their homes, break up their meetings, and vilify them night after night on the evening news.
Did we know we were lying about the drugs? Of course we did.”
~ John Ehrlichman, Assistant to the President for Domestic Affairs under President Richard Nixon
We have banned alcohol, religions ban alcohol. It's more to do with moral panic rather than subjugating people. As others mention, Singapore, China, Japan, North Korea, etc. have strict control over narcotic substances. Many countries are in diametric opposition to US policies but "agree" with narcotics policies for some of the same reasons.
You have to realize countries will make things terrible crimes by framing something anti-colonialist.
No doubt that was the case for many instances; however, I would posit that even if the US had been homogenously either black or white as a nation, in either case as a country we would still have controlled those substances. By and large, the only places that didn't control narcotics were locations with poor/weak central governments or a history of proscribed consumption (central Asia had/has a history where it's customary for older folks to consume, but it is heavily frowned upon for non older people to consume.)
It’s even more ridiculous when you learn that there is a prescription form of medical THC, fully legal and authorized under the FDA and DEA rules. And it’s a schedule III.