The US forced countries to criminalize the export of drugs to the US, even though though no country (the US included) has the resources necessary to enforce those laws.
The result is shadow economies, then corruption and finally narco states. This profits corrupt actors in the US government, so they perpetuate the cycle.
There are basically two sides in the war on drugs: almost everyone (non-users, users, small-time producers), and para-military syndicates that control distribution, enforcement agencies, and government policies.
If you read the article I linked, and also the one this thread is about, it is clear that the US decided to back one of the cartels with military aid and support in the local election. That caused a transfer of power that left 100,000’s dead, including the 43 students that were murdered by US-backed Mexican government officials.
Which policy do you mean? Not legalizing drugs? Because the US is no exception in that regard.