From the Document: "Taiwan, which officially calls itself the Republic of China (ROC), is an island democracy of 23.6 million people located across the Taiwan Strait from mainland China. U.S.-Taiwan relations have been unofficial since January 1, 1979, when the Carter Administration established diplomatic relations with the People's Republic of China (PRC) and broke formal diplomatic ties with self-ruled Taiwan, over which the PRC claims sovereignty. The Taiwan Relations Act (TRA, P.L. 96-8; 22 U.S.C. §§3301 et seq.), enacted on April 10, 1979, provides a legal basis for this unofficial bilateral relationship. It also includes commitments related to Taiwan's security. For discussion of economic issues, see CRS In Focus IF10256, U.S.- 'Taiwan Trade Relations,' by Karen M. Sutter."
CRS In Focus, IF10275
Congressional Research Service: https://crsreports.congress.gov/