Why doesn the United States have official diplomatic relations with Taiwan?
In the 1970s the United States sought to improve its relations with China. Because of the rivalry between the Chinese government and the Republic of China government on Taiwan, Beijing insisted that US-China relations could not be normalized unless the USA broke its relations with Taiwan. Accordingly, on Jan. 1, 1979, Washington ended formal diplomatic relations with Taiwan and established them with the People’s Republic of China. Since then US-Taiwan relations are handled through offices that are technically non-official.
Regarding the comment by “Jodie Yang,” note to readers: this topic tends to attract attention from paid PRC trolls. The comment gives you an idea of how Mainland Chinese feel about this issue. There are equally strong and opposite feelings in Taiwan, which helps explain why this has been such a intractable issue.
It is simply because China and USA agreed in 1972 that the US would not have relations with Taiwan. As far as China and US foreign policy is concerned, there is only one China and that is the one with the communist government.
From China’s point of view, Taiwan is not even a country. It is a runaway province. When Taiwan is going to return to China is unknown.