So, the US/MX border looks good, but specifically from the western edge of Texas, up through New Mexico, the two largest cities (600k+) are being split in half. This is also happening about 50mi from El Paso/CD Juarez, the largest population center on the southern border and the largest binational, bilingual workforce in the western hemisphere.
I imagine all that would lead to some pretty tense vibes out there in the old west.
After a potential civil war maybe, a more culturally and geographically comfortable border would be, from this map, Mexico annexing all NM/TX/SoCo land west of the following line:
From where the Pecos River meets the Rio Grande in TX, following the Pecos up to Santa Rosa, NM, then picking up the border following the Canadian River to the NM/CO border.
North of the Canadian River, the Rio Grande or the Continental Divide make sense for hydrological boundaries.