'anti-' originates from Greek, specifically the word 'anti' where 'anti-' meant 'against', combined with the English abbreviation 'US' (from 'United States').

'anti-' entered English via Latin and Old French from Greek 'anti'; 'United States' became commonly abbreviated as 'U.S.' in modern English, and the compound 'anti-US' developed as a hyphenated form in contemporary usage.

Initially it meant 'against' (the sense carried by the prefix) combined with 'United States'; over time the compound has retained the basic meaning of 'opposed to the United States' with little change.