"It is derived from America, a term originally denoting all of the New World (also called "the Americas"). It retains this Pan-American sense, but its usage has evolved over time and, due to various historical reasons, the word came to denote people or things specifically from the United States of America. In modern English, "American" generally refers to the United States, and in the U.S. itself this usage is almost universal, with any other use of the term requiring specification of the subject under discussion. However, this ambiguity has been the source of controversy, particularly among Latin Americans, who feel that using the term solely for the United States misappropriates it." Source