For those interested in details of the US-China Air Services Agreement, here's a link to the official documents:

Full List of Air Transport Agreements and Record Documents - United States Department of State

FEBRUARY 12, 2008 U.S.-China Diplomatic Notes No. 232 of February 12, 2008 & No. 245 of November 19, 2007
JULY 9, 2007 U.S.-China Air Transport Agreement of July 9, 2007
MAY 22, 2007 U.S.-China Initialed Aviation Liberalization Agreement dated May 22, 2007
MAY 22, 2007 U.S.-China Memorandum of Consultations
MARCH 15, 2007 U.S.-China Memorandum of Consultations of March 15, 2007
JULY 24, 2004 Protocol to the Agreement Between the Government of the United States of America and the Government of the People’s Republic of China Relating to Civil Air Transport
JUNE 11, 2004 Memorandum of Consultations Between Delegations representing the Governments of the United States of America and the People’s Republic of China
APRIL 8, 1999 U.S.-China Protocol to ATA of April 8, 1999
FEBRUARY 10, 1992 U.S.-China Amendment to Bilateral Agreement of February 10, 1992
SEPTEMBER 17, 1980 U.S.-China Air Transport Agreement of September 17, 1980

Wikipedia also has a good historical summary of the agreement including references to recent post-Covid developments.

Air route authority between the United States and China - Wikipedia

Would note that my interest in this topic is based on my involvement while working for United including participation on the PanAm-United transition team in 1986 and the startup of the PVG-SFO, PEK-ORD, PEK-SFO & PVG-ORD nonstops.