On the first day in 1979, the United States released this joint statement with China: “The Government of the United States of America acknowledges the Chinese position that there is but one China and Taiwan is part of China.”

The U.S. Embassy in Taiwan was closed and later replaced with the American Institute in Taiwan. This decision was a source of contention in Taiwan, and many protests took place.

You can read more about the decision to de-recognize Taiwan and the consequences of that decision at the link.