This does not explain the situation in Europe, South America or Asia, all of which have (or had) laws similar to the US for drugs.
all US-imposed policies.
For examples China under Mao, 'cured' the opium problem using extreme repressions [1]. Have you got any evidence that Singapore or Duterte's repression was requested by the US?
[1] https://en.wikipedia.org/wiki/History_of_opium_in_China#Unde...
Drug laws vary wildly in the regions you mentioned. Just about the only thing that they have in common is that drugs are illegal.
And it's not just a question of laws, either. Laws are one thing, and policing is another. There are countries which don't really enforce the law for personal use amounts.
The US has draconian laws, and punitive policing. There's your problem. It turns out that the worse you treat your criminals, the worse your crime problem gets.