'U.S.-supporter' is a compound of the abbreviation 'U.S.' (short for 'United States') and the noun 'supporter'. 'United' and 'States' come from late Latin/Old French roots for 'made one' and 'condition/standing', while 'supporter' derives ultimately from Latin 'supportare,' where 'sub-' meant 'under' and 'portare' meant 'to carry'.

'supporter' developed from Latin 'supportare' into Old French (soutenir/supporter) and Middle English forms (supporten, supporter) and later became the modern English noun 'supporter'. The abbreviation 'U.S.' arose in modern English after the formation of the 'United States' in the late 18th century and became commonly written as 'U.S.' or 'US'.

Initially 'supportare' literally meant 'to carry from beneath' (physical support); over time 'support' broadened to mean 'to back, to endorse, or to provide aid', and 'supporter' came to mean 'one who backs or endorses'. In the compound 'U.S.-supporter', the meaning specifies backing directed toward the United States.