The United States doesn't officially recognize Taiwan as a country. Taiwan is not a member of the United Nations. Apple's revenue in Taiwan is peanuts compared to that of mainland China. The list goes on.
That means little. The US has de-facto diplomatic relations with Taiwan, and has made official commitments to its defense against threats (which realistically could only ever come from the PRC), such as selling it arms. The weirdness and official ambiguity here are driven by the PRC's sensitivities, and do not represent any real commitment to the PRC's position.
Obviously, at some point realpolitik caught up and they reversed their stance, though they continue to help Taiwan because... more realpolitik.