China

Here are the documents mentioned, hosted by USC Annenberg:

• the three Joint Communiques
  • Joint Communiqué of the United States of America and the People's Republic of China, February 27, 1972 (Shanghai Communiqué)
  • Joint Communiqué of the United States of America and the People's Republic of China, December 15, 1978
  • Joint Communiqué of the People's Republic of China and the United States of America, August 17, 1982
• Taiwan Relations Act
  • Taiwan Relations Act, 1979
• the Six Assurances
  • Congressional Research Service, Pres. Reagan's Six Assurances to Taiwan [in 1982], October 8, 2020

1972 Joint Communiqué

12. The U.S. side declared: The United States acknowledges that all Chinese on either side of the Taiwan Strait maintain there is but one China and that Taiwan is a part of China. The United States Government does not challenge that position. It reaffirms its interest in a peaceful settlement of the Taiwan question by the Chinese themselves. With this prospect in mind, it affirms the ultimate objective of the withdrawal of all U.S. forces and military installations from Taiwan. In the meantime, it will progressively reduce its forces and military installations on Taiwan as the tension in the area diminishes. [...]

1979 Joint Communiqué

2. The United States of America recognizes the Government of the People's Republic of China as the sole legal Government of China. Within this context, the people of the United States will maintain cultural, commercial, and other unofficial relations with the people of Taiwan.

3. The United States of America and the People's Republic of China reaffirm the principles agreed on by the two sides in the Shanghai Communique [...]

7. The Government of the United States of America acknowledges the Chinese position that there is but one China and Taiwan is part of China.

1982 Joint Communiqué

(1) [...] the United States of America recognized the Government of the People's Republic of China as the sole legal Government of China, and it acknowledged the Chinese position that there is but one China and Taiwan is part of China. Within that context, the two sides agreed that the people of the United States would continue to maintain cultural, commercial, and other unofficial relations with the people of Taiwan. On this basis, relations between China and the United States were normalized.

Note that some have played around with the word "acknowledge" and say that to acknowledge something does not imply agreeing with it, which can technically be true, but I think that is a gross misuse of terminology with regards to important diplomatic relations.