Wishful thinking that these cartels would simply pack up and go home if we (the US) legalized one of their products. Even if we legalized all of their products I doubt they'd throw their hands up and find legitimate honest work.

I suspect they'd find a new illegal business to run, more people to extort, murder and threaten and continue on as before.

One thing about that is that if it was suddenly announced overnight, the value of weed could crash. Given that a lot, if not most, weed trade is on credit, (they take the weed, pay the supplier once its sold on,) most dealers would be left with debt and devalued weed to try to settle it. Actually could get rather nasty.