<< While white people can never become black, >>
Actually this is not true. I had the reverse happen to a friend, and it could happen to her again in reverse. I went to grad school in England, where Indians (from India) are black--Little Black Sambo is an Indian, remember the tigers? Anjali is a veddy veddy uppah clhass Indian, her family would have Indira Gandhi to tea, that sort of thing, but as a grad student in econ at Cambridge she was just another n-word. She moved to the states when she finished her degree to work for the World Bank (boo hiss), where she is now a senior economist and thetoken advocate of increased state intervention in theeconomy on the Bank. But whens he arrived she visited my parents in law in NYC, who loved NY, especially its obscurer bywayts, and would regilarly go where no white people had ever gone. They too Anjali and my wife to a show waayy up in Harlem, and they were the only non-African-Americans in the large audience. The playwrite met with the interested after the sho and when my in-laws,. A, & spouse came up to shake her hand, she hesittaed and asked pointedly, and how did YOU come here? A said she realized at that moment that she had gone from Brahmin (in India) to black (in England) to white, more or less, in America. If she went back to England, she'd be a wog nig nog again.
Or again, Adrian Piper, the philosopher and conceptual artist was one of my Kant teachers at Michigan. She is 1/8 black, but looks maybe Italian or Jewish. She went to Harvard on some kind of minority scholarship, and there is a story about her that a famous reactionary philosophy prof came up to her, somewhat sloshed, at the meet-the-new-grad students party and slurred, "You don' look any blacker'n I am."
The point: "black" is cultural more than it is biological. Who is "black" depends on who a society has oppressed. The Brits oppressed Indians,s o they're black. We didn't--not Indian Indians, so they're not--for us. Adrian is light enough to "pass," so the reactionary jerk resented her getting a minority scholarship.
Karl Lueger, the antiSemitic mayor of fin de siecle Vienna, who nonetheless had rich Jewish friends, used to say, Wer ist ein Jude, ich bestimme. Who is a Jew, I determine.
There is a book called How the Irish Became White. the Jews did too, here. They didn't use to be so regarded.