US CODE: Title 28,3002. Definitions (15):
(15) “United States†means—
(A) a Federal corporation;
(B) an agency, department, commission, board, or other entity of the United States; or
(C) an instrumentality of the United States.
http://www.law.cornell.edu/uscode/html/uscode28/usc_sec_28_00003002----000-.html
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