It does seem that most heroin consumed in the US originates in Mexico currently. However it is true that Afghanistan helps supply most (as in <90%) of the world

It does seem that most heroin consumed in the US originates in Mexico currently. However it is true that Afghanistan helps supply most (as in <90%) of the world's heroin, and their production is much greater than Mexico and South America as well. > The vast majority of worldwide poppy for opiates is Asia, but the US is unique in that most of the poppy source for their heroin is coming from Columbia and Mexico. It is odd. I think this is a signal that Mexican cartels have monopolized American markets. Smaller unaffiliated players are more likely to use trans-Pacific supply chains. It also seems that the cartels have vertically integrated their operations such that they now grow opium poppies and aren't reliant on South American countries for raw materials.