"How could Juan been African American if there was no America? Not like he had a passport to change over."
He was the first person of African origin (and he was Portuguese before being Spaniard tbf) to set foot in America, and not only that, but also settling and dying there of "old" age at fifty something years old and the rank of Captain)
Back in those days people have their "Probanza de Meritos" or "proof of merits/deeds" which where basically a mix of a diary, curriculum vitae, and you guessed it, passport (there weren't nations as we know them today, but there were large kingdoms that sat the basis for later absolute monarchy states, which then gave our modern nations, but you still had to prove where you were from, specially if you looked so different, and that's because racism as we know it today is a modern invention, what happened back then was simply xenophobia, and it's just that the more different you looked, the easier it was to tell that you were not from around here, and thus not worthy of too much trust at first, hence why probanzas where such invaluable documents).
Probanza means literally "to prove", literally the document with which you prove to be who you say you are.