U.S.-China trade volume was negligible until well into the 1990s: https://www.weforum.org/agenda/2019/05/more-than-30-years-of.... By 1995, Singapore’s GDP per capita had already overtaken the UK’s.

Trade was obviously important to Singapore’s development. But the idea that it was just because Singapore happened to be Singapore’s location relative to China is anachronistic. Singapore’s annual GDP per capita growth was already over 15% by the time Nixon went to China in 1972. It actually started slowing down by the 1990s when China’s growth started picking up.