How come in most school in the USA (at least mine) they teach Spain Spanish instead of Mexico Spanish? Would not Mexico Spanish be an obvious choice to teach?
Maybe it's because I'm from California, but we learned Mexico-Spanish. The books included Spain-Spanish (i.e. vos conjugations), but my teachers never included it in our lessons.
I had a teacher from Spain for three years, then for the next four years they were from various countries: Argentina, Colombia, Mexico, and the US. It was great to get used to each accent.