The Magical Congress of the United States of America (MACUSA) is the governmental authority for the Wizarding world in the USA (Pm, WFT). The headquarters of MACUSA is hidden in the Woolworth Building. The emblem of MACUSA features an American flag combined with a phoenix (WFT). MACUSA is a single body, unlike the Muggle two party system (JKR:Tw). The president in 2014 was Samuel G. Quahog (Pm). The MACUSA employs Aurors, just like the Ministry of Magic does in the UK. Percival Graves and Porpentina Goldstein were Aurors for MACUSA in the 1920s (WFT).
An extension of the name of the Congress of the United States of America. Unlike the magical body, the US congress consists of two houses: the House of Representatives and the Senate.
From the Web
Pottermore: History of Magic in North American by J.K. Rowling
Pottermore: Magical Congress of the United States (MACUSA) by J.K. Rowling