In fact we do use the word “aliens” for those who come legally.
Internal Revenue Code Sec. 7701(b)
(b) Definition of resident alien and nonresident alien.
(1) In general.
For purposes of this title:
(A) Resident alien. An alien individual shall be treated as a resident of the United States with respect to any calendar year if (and only if) such individual meets the requirements of clause (i), (ii) , or (iii) :
(i) Lawfully admitted for permanent residence. Such individual is a lawful permanent resident of the United States at any time during such calendar year.
(ii) Substantial presence test. Such individual meets the substantial presence test of paragraph (3).
(iii) First year election. Such individual makes the election provided in paragraph (4).
(B) Nonresident alien. An individual is a nonresident alien if such individual is neither a citizen of the United States nor a resident of the United States (within the meaning of subparagraph (A) ).
I know and I caught that too.