The limit citizenship to "free White persons of good character" founding fathers [1]? Or Thomas Jefferson, who considered that, when freed, Blacks should be "removed beyond the reach of mixture" [2]? James Madison, who wrote "To be consistent with existing and probably unalterable prejudices in the U. S. the freed blacks ought to be permanently removed beyond the region occupied by or allotted to a White population." [3]? Or Benjamin Franklin, writing "the Number of purely white People in the World is proportionably very small [..] I could wish their Numbers were increased [..] But perhaps I am partial to the Complexion of my Country, for such Kind of Partiality is natural to Mankind." [4]?
As an American you were probably exposed to much propaganda about how the US is a "nation founded on an idea", or similar nonsense. But as a foreign observer, let me assure you nothing could be further from the truth. Did you never ask yourself, if the founders were such racial egalitarians, how is it that, aside from the descendants of Black slaves (10%), the US was nearly entirely white (87.5%) until 1950? That leaves just 2.5% for immigration from the entire rest of the world.
[1] https://en.wikipedia.org/wiki/Naturalization_Act_of_1790
[2] https://www.theatlantic.com/magazine/archive/1997/03/what-je...
[3] https://press-pubs.uchicago.edu/founders/documents/v1ch15s65...
[4] https://founders.archives.gov/documents/Franklin/01-04-02-00...