I think the issue is about the unintended consequences (or maybe intentional for some of the more right wing) of the war on drugs, compared to other ways of dealing with this issue that have shown some promise - like Portugal's experiment with legalization of all drugs with rehabilitation taking precedence over incarceration.

In the U.S. this change, along with three strikes laws, etc. has resulted in another round of "Jim Crow," because the law is applied in a racist manner.

The issue of cultural racism applies for Bolivia as well.

And the violence that has been part of an escalation of the war on drugs in Mexico is causing harm to that nation.

One reason I think the U.S. wants to continue the war on drugs as it does is because, like the agriculture dept and its budget, money allocated to the war on drugs can also go to right wing groups within a nation to undermine self-determination - I think that's also part of the issue for Latin American nations with the long, long history of the U.S. interfering with their governments because of the cold war fears of social democracy rather than the right-wing authoritarian regimes the U.S. has traditionally endorsed there.