The roots of this particular fiction date to 1949, when Chiang Kai-shek’s Republic of China was routed by Mao Zedong and the Communists, and Chiang fled to Taiwan. The U.S., in Cold War mode, continued to recognize the ROC in Taiwan as China’s rightful government, and so did the United Nations. But in 1971, the UN changed course, recognizing the People’s Republic of China—or as it was often called then, Red China—as the legitimate government. In 1979, the United States followed suit. Crucially, the communiqué proclaiming that recognition noted, “The Government of the United States of America acknowledges the Chinese position that there is but one China and Taiwan is part of China.”
Officially, this has also been the policy of Taiwan for almost a quarter century. Under the 1992 Consensus, another artful diplomatic fiction, both Taipei and Beijing agreed that there was only one China and agreed to disagree on which was legitimate, as well as maintaining two separate systems. During the Bush years, the U.S. said it would defend Taiwan in an attack, but Bush also pushed back on Taiwanese moves toward independence.
Despite recognizing the PRC, the U.S. has kept close ties with Taiwan since 1979. The State Department notes that “Taiwan is the United States’ ninth largest trading partner, and the United States is Taiwan’s second largest trading partner.” More importantly, the U.S. has sold some $46 billion in arms to Taiwan since 1990, which are intended as defensive. Last December, the Obama administration sold $1.8 billion in anti-tank missiles, warships, and other materiel to Taipei. Of course, the “defensive” purpose to all of this is against China, the most plausible aggressor against Taiwan. Naturally, the arms sales have consistently annoyed the Chinese. (Recently, China has been on a campaign of land-grabbing and saber-rattling across the South China Sea, trying to assert greater control and influence.)