Final answer:
The US supported the Republic of China (Taiwan) until the late 1970s, politically, militarily, and economically, due to Cold War politics. Taiwan represented China in international bodies like the UN until 1971. The US shifted its recognition to the People's Republic of China (Mainland China) after diplomatic efforts in the early 1970s.
Step-by-step explanation:
The United States supported the Republic of China (Taiwan) up until the late 1970s. Following the Chinese civil war, which resumed after World War II, the US sided with Chiang Kai-shek's Nationalists, who fled to Taiwan after being defeated by Mao Zedong's Communist forces. The US recognized the government in Taiwan as the legitimate government of all of China, as it opposed the Communist government that declared the People's Republic of China (PRC) on the mainland. This support included political backing, military assistance, and economic trade. This stance was maintained until the 1970s when the US began to shift its diplomatic recognition to the PRC under Mao Zedong.
Until 1971, Taiwan represented China at the United Nations, illustrating the significant international support that the Republic of China enjoyed. This policy was partly due to Cold War politics, which saw a strategic interest in supporting Taiwan against Communist China. However, after diplomatic efforts by President Nixon in 1972, the US eventually recognized the PRC as the legitimate government of China.