Sentence:  Nonresident aliens living in Canada or Mexico who earn wages in the United States may be subject to withholding of tax on their wages , the same as if they were citizens of the <WSD>United</WSD> States . 
Meaning of the word marked with <WSD> tags:  North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776