Answer: They’re both composed of human beings.
They both have millenary cultures.
They both suffered under european imperialism.
Their native populations both have genes in the A haplogroups (although Mexico is actually about half R1b dominant).
They both had advancements in math (and Astronomy, in Mexico’s case) that matched or exceeded what was available in Europe at the time.
Ah, maybe one more. There’s a lot of chinatowns in Mexico because Mexico has always had Chinese in-migration, but one in particular is the largest: Mexicali, Baja California, is a very chinese city in Mexico.
Other than that, everything else is different. Everything.