It's an interesting manifesto. Not as dumb as I expected. Smart enough to convince someone inclined to think that way and not to find fault.
Unfortunately, no American has standing when it comes to immigration as that was one of its original colonial purposes. If your argument disqualifies immigration, then there ought to be no USA. Not a strong argument.
The idea that whiteness is a thing of the sort he describes is also bogus. A brown-skinned Indian is as much an Indo-European as a white European. An African is as much a homo sapiens as we all are: that's the homeland of our ancestors. There's nothing distinct on this scale about native Americans, including the Mexican peoples, but they were here in the Americas before the white people of northern Europe.
All the same, we are all mutts. I am a mutt and celebrate my ancestry as a mutt of the English variety.