Well, that's not what it implies.
The adjective describes the type of American. I'm German/Polish- American. I just say "American." The majority of people here just say, "Black guy" or something but I wouldn't say "African American" unless someone preferred it.
I used to call my ex-white girlfriend an African American as she was from the RSA.
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To clarify, my ex-girlfriend, who happened to be white.