US law prohibits discriminating based on national origin except under specific circumstances. https://www.law.cornell.edu/uscode/text/8/1152

(A) Except as specifically provided in paragraph (2) and in sections 1101(a)(27), 1151(b)(2)(A)(i), and 1153 of this title, no person shall receive any preference or priority or be discriminated against in the issuance of an immigrant visa because of the person’s race, sex, nationality, place of birth, or place of residence.