hi; just ran into your post while searching for something else. You may be interested in these posts on the concept of "white" in the USA
How did the concept of "whiteness" as a racial identity develop and change over time?
When and how did ethnic groups such as Irish and Italians become "White"?
Were Irish people white...in the USA in 1931? (cross-posted from AskReddit)
Before the Irish became "white" in the US, how were people able to distinguish them as "non-white?"