noun
Refers specifically to the bicameral legislature of the United States, consisting of the Senate and the House of Representatives.
アメリカ連邦議会は上院と下院から成る。
The US Congress consists of the Senate and the House of Representatives.
その法案はアメリカ連邦議会を通過した。
The bill passed the US Congress.
国会 is the generic term for a national legislature, often used for Japan's Diet. アメリカ連邦議会 is the specific proper noun for the US Congress.
Compound of アメリカ (America) + 連邦 (federation) + 議会 (parliament, congress). A straightforward calque for the United States Congress.