The nub here is that these people are described or classified exclusively according to racial, national, or ethic origion, with no regard nor recognition that many, while still "Mexican" or "Japanese" in heritage, if not appearence, are nonetheless American in nationality,citizenship, and actual residence. The head, in effect, makes them permanent aliens. 

Indeed, when rigorously employed solely within the United States context itself, no "people" apart from Amerindians justly qualify for the un-hypenated AMERICAN.

Sanford Berman, Prejudices and Antipathies, 1971, p. 31.