The US and China established full diplomatic relations in 1979, but that year the US Congress wrote its own script for Taiwan. Today, what the Chinese side interprets as word games by the US may wreak deadly consequences. 

As the pressure heats up over Taiwan there seems to be some confusion about the terms on which the US is supposed to have recognised China.

https://johnmenadue.com/china-taiwan-and-the-us-the-real-terms-of-the-deal/