Why is it okay with the Big Zero that trucks driven by Mexican citizens are okay in the United States, but trucks driven by American citizens aren't okay in Mexico?
It's my understanding American and Canadian truck drivers have to hand over their trailers to Mexicans at the border, as they aren't allowed to carry freight south of the Rio Grande.
Not that any of them might want to, given the anarchy and corruption of the Mexican highways, but it appears they can't even if they wanted to.