From the Background: "The proposed United States-Mexico-Canada Agreement (USMCA) would revise and replace the North American Free Trade Agreement (NAFTA), in force since January 1, 1994. NAFTA eliminated trade and investment barriers between the United States and two of its largest trading partners, Canada and Mexico. It was the most comprehensive free trade agreement (FTA) negotiated at the time and contained groundbreaking provisions in areas such as market access, rules of origin (ROO), intellectual property rights, services, investment, dispute settlement, and worker rights. The North American motor vehicle industry is highly integrated and is a major source of trade and investment among the NAFTA partners. On December 13, the Trump administration submitted to Congress the proposed USMCA implementing legislation, which reflects the recent amendments. On the same day, the United States-Mexico-Canada Implementation Act (H.R. 5430) was introduced in the House of Representatives. On December 16, the bill was introduced in the Senate (S. 3052)."
CRS In Focus, IF11387
Congressional Research Service: https://crsreports.congress.gov/