The Mexican cartels in general tend to avoid heat directly from the United States government and them establishing themselves here in the U.S would get them more heat because of the exposure retail drug sales tend to give off. In many a lot of the fighting between the groups (Mexican TCO) are primarly for retail drug sales and the profits that come with the territory. If the cartels abandoned retail drug sales in the Mexico much of hte violence you see today will stop. Well at least among the TCOs but they won't because retail drug sales in Mexico is worth around 1 billion dollars. As the cartels started to sell drugs on the streets, their membersip exploded and they are now much more numerous than before.