Usa policy towards taiwan vs china relations

Modern history of Taiwan, which at different points of history belonged to Dutch and Japanese starts in 1949, when Chiang Kai-shek lost in the civil war on the mainland, and fled to Taiwan, where he established his regime and considered his government in Taiwan as official and ruling over China.
The population of the island that time mainly consisted of 85% of native Taiwanese and only 15% constituted Chinese mainlanders who came over with Chiang Kai-shek. Through the tight control of the political system, police, military, educational system and media they managed to control predominating native population.
Officially Japan gave up its sovereignty over Taiwan in 1951-52 by concluding the San Francisco Peace Treaty. The importance of the treaty that with lost control of Japan it was not determined who was the beneficiary and it was stated that “…the future status of Taiwan will be decided in accord with the purposes and principles of the Charter of the United Nations.”
Hence, according to the right of self-determination specified in the Charter of the UN, article 1.2 people of Taiwan has right of self-determination, and therefore can decide themselves to which country belong or whether to be an independent state.
Later on, in 1971 with opening US diplomatic relations with China and Taiwan loosing its representative status of all China in UN, US policy makers acknowledged China position on