How does having a PhD from Latin America impact an academic career in mathematics in the US?
The institution from which you have a PhD is of minor significance compared to:


What you've published
Where you've published
Who you've published/worked with (particularly, your advisor)
Who can recommend you to others


With all of those being equal, a PhD from a better-rated university (not country) will improve your evaluation as a candidate to some extent, I suppose.

However, I believe you're thinking about this the wrong way. I would suggest trying to find specific potential post-doc hosts - researchers whose work is related to what you are interested in - and contacting them directly rather than thinking of "applications" in the general and the abstract.