Listen, Delbert Dumbunny, whoever these latest guys were, they crossed over the Rio Grande, which defines the border between much of Texas and Mexico. They had to know that they were in the U.S. Moreover, they took up defensive positions to shield the smugglers they were protecting while they hauled their marijuana back South after being discovered. This was no, "Whoops, we should have hung a left on Avenida de la Playa" mistake.
We can settle the issue of "were they real military" by running the VIN of the hummer they abandoned and burned on the U.S. side. If it was sold to the Mexican government, we have our answer.