Yeah, that’s the ticket. Convince Mexicans that the best way to end drug violence is to sell off large areas of their country to foreigners. I’m sure they’ll jump all over that plan.
Here's the more positive, affirmative approach. As an aside, you do realize that anyone can buy/finance/insure any property in the USA, UK, France, Italy, etc, right? Or, in your words, sell off "their" countries to foreigners? That's what happens when you have free capital flows and legal investment protections. The result is $trillions of value in cross-border trade and economic growth.
MX has an artificially constrained economy. It's based on the convenience of maintaining the status quo by Castilian Spaniards controlling the game. They've got property rights tied up so that no one can move, leverage or invest. In this way, the ruling class keeps the 90% peasant population impoverished and willing to engage in subsistence farming and other sub-optimal activities, including low level drug trade.
Everyone is happy with this arrangement: the banks, including US banks, MX politicians and business owners, US interests in maintaining drug/migrant flows (ie deep state/DNC/GOPe). The only down-side is when we get a story like this, along with the usual million or so drug overdose/addiction cases occurring on an annual basis.
So, everything is great as long as no one gets too upset about occasional collateral damage. Lots of talk, lots of outrage, but then it all settles down again. Been this way for hundreds of years. Problem is, populations are growing, so the downside effects are becoming harder to contain.
The only way for the problem to be actually "fixed" is to break the hold the Spaniards have on MX society, culture and economy. To do that, the country has to join all the other advanced & developing countries that allow free capital flows. For Japan and China, that means factories (yep, "selling out their countries"). For London, that means real estate and global banking access.
For MX, well, they are literally the global beauty queen in terms of both weather and territory. If you could actually acquire a direct ownership, back it with a mortgage, title and homeowner's insurance, the place would take off like a rocket. That's the key, so all one has to do is watch the bouncing ball. Trump plays a military card, forget it. Trump plays the cartel suppression card along with open investment opportunities, and MX can finally be a capable, worthwhile southern neighbor.