system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 : Why do people in the US use the term "African American" when they mean black people ?

There are white african americans, and not all black people are actually originally from Africa.  
I've actually heard Americans visiting my country use the term "african americans" when they meant black people in *my* country and everyone in the conversation was puzzled on how people can get it so twisted.  

ELI5 : if white people are white, why are black people "african americans" ?
gpt
In the 60s and 70s during our civil rights movement here in the US blacks as a whole, or at least the vocal civil rights activist decided that "black" was too close to the pejorative "colored" and so decided that the politically correct ethnic term they wanted to use was "African-American". 

And save for the Aborigines of Australia and a few of Polynesian island natives all blacks do trace their lineage to Africa. Particularly those here in the US. But because of slavery African-Americans cannot trace their ethnic groups to specific tribal/ethnic groups like whites can (Italian-American, Irish-American, German-American) so they chose to refer to the continent of origin.