Just remember: An alien is anyone who comes from outside your country...like Mars for example. Or Mexico.
A non-resident alien for tax purposes is a person who is not a U.S. citizen and who does not meet either the “green card” or the “substantial presence” test as described in IRS Publication 519, U.S. Tax Guide for Aliens.
https://international.umw.edu/inter...esident-of-nonresident-for-tax-purposes/