> The United States always needs an enemy. Hitler, communism, Russia, Viet Cong, acid rain, drugs, them...
Not really "the US" per se, but the lobbies behind politics (the police likes the war on drugs because they get massive federal grants for it, and equipment resellers are happy to oblige - and where there is big money, there are influencers to make sure politicians go a certain way) in order to thrive.
Add to that that the public opinion is pretty much against drugs in America, and it's fairly straightforward for politicians to double-down on that kind of topic and enforce rigidity.