Answer: Near the Rio Grande in the eastern portion of MexAmerica and the Arizona portion of the Colorado River, in the western part of the region
Explanation:
The Rio Grande is a physical boundary that simply separates United States from Mexico. It should be noted that more precipitation are gotten in Eastern MexAmerica.
The main center of agriculture in MexAmerica are located near the Rio Grande in the eastern portion of MexAmerica and the Arizona portion of the Colorado River, in the western part of the region.