• You may be interested in my recent answer where I talk about the abolition of slavery in 1829, shortly after Mexican Independence. It also deals with the earlier colonial context and esp. with African slaves fleeing to Mexico.

• In this follow up I discuss [ways in which Afro-Mexicans have been and continue to be marginalized] (https://www.reddit.com/r/AskHistorians/comments/9y8sv8/why_do_méxico_and_argentina_have_low_populations/e9zvcnp?context=3), relating to your second question.

I haven't studied the US much so can't give you a detailed comparison. But a few key differences between Mexican and US emancipation do come to mind:

At least initially in colonial Mexico most African slaves worked in households, different from chattel slavery. - - The importance of slavery had diminuished by later colonial times, so that the abolishment had less concrete consequences. - - All this also has to do with the intermixing between Europeans, Africans and Native Americans since the beginning of the colonisation in Mexico, which made it harder to uphold clear racial barriers (as described above): so quite a different thing from the One Drop Rule.