While it’s true that the U.S. is the most convenient market for Mexican cartels, it’s worth knowing that it’s far from the only one. Mexican drug cartels have major connections to markets across the globe. and that Mexico specifically is the de facto administrator of drug trade in the western world. For example, a drug bust in India found fentanyl that had been purchased in Mexico from China. . That’s not the sort of arrangement that the US can ever hope to do away with through domestic legislation without undermining the autonomy of dozens of states around the globe.
While removing the cartels’ access to the American market via decriminalization would certainly take away a lot of funds, let’s not act like black market operations don’t exist in legal markets anyway.
In this hypothetical situation where the US is responsible for Mexico’s drug cartel problem (which I disagree with), I don’t think the road to success ends at the US legalizing drugs.