The relationship of whitened vis a vis blackness and its importance to justifying lifetime, inherited, Chantal slavery is, I think, very well understood by this crowd.
But whiteness had many uses and not the least among them was simultaneously excluding any other foreign peoples from a claim on the United States and also justifying the mistreatment of the people who were already here.
Texts from the times of aggressive westward expansion are replete with the notion that the white man (at that time Anglo-Scottish and occasionally German - notably not French or Spanish) was the pre-destined conqueror of the continent. There are lame justifications such as efficient use of the land or bringing “civilization” but then, as now, the reason followed the conclusion. Any argument that supported the notion of that white men were true Americans was taken as principle no matter how unprincipled it might be.
So the white myth has already anticipated and foundation ally rejects any notion of birthright from Native Americans.