We just barge that shit down the river...DUH!
I doubt many DUpipo realize that ~ half the US border with Mexico is the Rio Grande River, with several significant cities along its course. Westward from El Paso, NM's SR9 and SR81 follow most of the border with NM closely. There's a ~70 mile gap from Antelope, NM to where US 191 meets the border in AZ. Then from Douglas to past Miracle Valley AZ SR80 and SR92 are close to the border. There's a ~25 milgap from Miracle Valley to Lochiel, AZ, then a county road goes through Kino Springs and meets SR82 that goes into Nogales. There's about a 100 mile gap from Nogales to where SR85 goes through Organ Pipe National Monument, and maybe a 90 mile gap from there to Yuma near the borders between Mexico, AZ, and CA. Westward from Yuma, I-8, I-805, SR98, and SR94 make it so there is one gap of less than 15 miles with no apparent roads on the CA side of the border.
I know, TL,DR, but my point is that a few minutes on Google maps would have shown
DU-Super-Genius Recursion his/her logistics argument is a non-starter.