Another commenter posted this link, https://www.washingtonpost.com/news/volokh-conspiracy/wp/201... , but it makes the convincing case that that was never true. Italians, Spaniards and Greeks we're always considered white in the ways the actually mattered in the US. They could drink from "whites only" drinking fountains. They could marry folks of British descent and nobody considered this an "interracial marriage". They could join unions that had "whites only" membership policies.
Another commenter posted this link, https://www.washingtonpost.com/news/volokh-conspiracy/wp/201... , but it makes the convincing case that that was never true. Italians, Spaniards and Greeks we're always considered white in the ways the actually mattered in the US. They could drink from "whites only" drinking fountains. They could marry folks of British descent and nobody considered this an "interracial marriage". They could join unions that had "whites only" membership policies.