Barack Obama has around 50% of his ancestors from Africa, most 'black' americans have a lot less than that. Example: if one of grand parents is black, one of your parents is, so you're black.

This is know as the one drop rule, if one of your ancestors is black you are black. So maybe 95% of your ancestors are from Europe and you are still considered as black.

Latin has even a fuzzier definition. Latin american countries have been build -as the US- with immigration. Immigrants from latin american countries are white, black, asian, etc... Or whatever classification the USA might invent. There is no less diversity in the rest of the Americas than in the USA.