The US policy was more nuanced than you suggest. The US never agreed to One China, the US just said it wouldn't challenge it. This is the exact text of it in th

The US policy was more nuanced than you suggest. The US never agreed to One China, the US just said it wouldn't challenge it. This is the exact text of it in the 1972 Shanghai Communique. the United States acknowledges that Chinese on either side of the Taiwan Strait maintain there is but one China and that Taiwan is a part of China. The United States does not challenge that position.