Deleted member 67076
Would Mexico be able to keep the area in question?
It's really big, far from Mexico City, and communications and effective governance would be rather difficult. Plus, Americans will be constantly pushing across the borders to settle.
Eventually I suspect we'd see either a war and annexation resulting from Mexican efforts to suppress settlement, regions breaking away from Mexico to eventually seek admission to the Union, or areas declaring themselves autonomous States which eventually become little but American satellites.
Not trying to burst any bubbles here, but that's how I see it.
Yes, send in settlers from the south and import immigrants to counter the American settlement. And crush any revolts that pop up.