Here is how I see a lot of this. If you hang around the latin community there are clear cut differences, acknowledgement, and respect there. In fact they probably think you're mildly retarded if you don't get it.
That's not Mexican, that's Puerto Rican. They are speaking Spanish but they are from Argentina. Then you have Guatemala, Honduras, Cuba. Then you have Chile and numerous other places, too many to name.
All of them are acknowledged, respected, and known to be different from each other. It's a big tent if you will.
Yet, if you are talking about the general purpose American Black Community, if you are a slight shade of brown all the way to dark as night you are ONE THING. Black.
Who cares if you come from a different culture, Island, tribe, language group or anything else. Our definition is supposed to fit you and you better be happy about it. In general you have to be intentionally stupid to 'be black', but the reality of it is that's a bunch of bullshit and everybody else knows it.
Hence a big reason why all of these other people don't like American Niggas.