The black population of the US is unquestionably descended from immigrants.

1.4% of the U.S. population is "American Indian and Alaska Native alone". 2.9% is "alone or in combination with another race" per the 2020 census.

I have no idea what you're going on about.

Slavery and indigenous are not considered immigration. You might want to study again about this.

Being multiracial, and of indigenous ancestry, does not necessarily mean or always count as immigrant. It is nebulous. No definitive conclusions, in regards to immigration, is made about those of mixed and indigenous ancestry. Speaking of mixed ancestry, the US has a very significant percentage in that category, from both the census and DNA testing.

There are also Canadian and Mexican indigenous people, who refute or argue about immigrant status, regardless of their present citizenship. Making the argument that their people were already in America or pushed out of their lands.