[toasterlovin]

FWIW, I have never encountered the concept of the "American race". Are you sure it's actually a thing? To me the line from American Dad's theme song seems like a joke (since America has many races).

[ScottFree]

According to Webster's 1828 dictionary

AMER'ICAN, noun A native of America; originally applied to the aboriginals, or copper-colored races, found here by the Europeans; but now applied to the descendants of Europeans born in America.

[toasterlovin]

That's nice, but:

1. It's a definition for the word 'American', not the phrase 'American race'.

2. It's from 1828. I don't think usage from 190 years ago is very relevant. Language changes pretty quickly.

3. That does not match what OP was talking about. They were talking about a further distinction within white Americans. Unless I'm mistaken.