Just because you never heard it doesn't mean it didn't happen. For example, Irish people were heavily discriminated against in the US and were considered at one point to not be "white"

https://thesocietypages.org/socimages/2008/10/06/negative-st...

https://en.wikipedia.org/wiki/Anti-Irish_sentiment

> Irish people […] were considered at one point to not be "white"

This isn’t true. Naturalisation was limited to white people and no Irish person was ever denied it in account of their race.