also antiamerican, 1773, in reference to British parliamentary policies, from anti- + American. As a noun by 1788. Related: Anti-Americanism "opposition to what is distinctly American" (1844).
The term "anti-American" is a loose one, and loosely employed. My own working definition of it, admittedly a slack one also, is that a person is anti-American if he or she is consistently contemptuous of American culture and furthermore supports any opponent of U.S. policy, whoever this may be. [Christopher Hitchens, review of "The Life of Graham Greene, Vol. II," The Atlantic, March 2005]