The US should focus on defunding them and any local support but by no means should the US do anything on Mexicos soil. Legalizing and regulating drugs locally would cut a lot of their funding I imagine. Long term it would also probably help the immigration numbers as well. Especially is we placed tariffs that enticed companies to not ship products from China but rather if they must use labor elsewhere to make it more profitable to move their manufacturing from China to Mexico/South America. It would help the regions and decrease shipping distance cutting back on environmental impacts.

Edit: typo, defunding became defending