Another idea would be to do the equivalent of Ronald Reagan’s star wars.
What would be the equivalent thing.
Place it as a national goal to collapse the cost of water desalination and transport. so that all deserts within 1000 miles of any seacoast could have fresh water cheap enough for farming brought from the coasts.
Once done that would effectively increase the size of the USA by about 1/3. But it would also triple the size of Mexico.
Mexico suddenly becomes a much richer country and a better destination.
The USA would not have a poorer neighbor to the south.
And the cartels would take over water distribution. A nation's wealth is predicated not only on its natural resources, but on the freedom of its people to develop them. If wealth were based on natural resources alone, Africa would be perhaps the wealthiest continent on earth.