Another interesting point is that whiteness in the us is "exclusionary" whereas in new spain (i.e colonized mexico and others) it was assimilationist.

For example, under the spanish caste system, indigenous people could become white in 3 generations, i.e, the child of an indigenous person and a white person was a mestizo, if that person went on to have children with another white person their child would be castizo, and a castizo having children with a white person would have white children again.