There are lots of "white" southerners who have Black ancestors. A lot of them refuse to admit it. I'm pretty sure the small percentage of my ancestry that's not documented has some Black lines in there. (My great aunt was a genealogist, so I'm ridiculously documented.)
When I was growing up in Illinois, I just assumed everyone whose family has been here for awhile has some NDN ancestors. In my case, the side of my family that isn't made up of recent Irish immigrants has a couple branches of the family tree with darker people of unclear origins. Add in family stories about various NDN friends and neighbors, all mixed in with the stories about blood ancestors and I grew up assuming some of my ancestors were NDN.
Then about ten years ago we found out that line of the family wasn't NDN... they were Jews! Ha! Jews who married Irish people and hung out with NDNs, but... Jews.
It didn't change anything for me. Since they fully assimilated into the Irish family they married into, no one really knew what their culture had been. While it's sad they had to hide who they were, I also think it's oddly funny. I could be an Adult Onset Jew! ... Nah.
On another branch I have Ross and Harris ancestry, so I have a ton of NDN *relatives*, but it's unclear whether I have any NDN *ancestry*. The names of my ancestors that are on the Dawes rolls are really common names. (William and Mary Ross), and there are multiple people with those names who were the right age. While it's interesting, I haven't really pursued it because, again, I didn't grow up in any NDN culture and neither did my parents, grandparents, or great-grandparents.
I'm glad I grew up assuming I had some NDN ancestors. I think it gave me a feeling of responsibility to support NDN political causes, and a sense of solidarity with Indigenous struggles. But I always knew I wasn't NDN. And I think people who believe they can change their ethnicity are pretty bizarre.