Some countries often have issues due to a lot of factors. The problem made China reluctant to improve relations with the United States is American support for Taiwan.
But the United State did does support Taiwan's membership in the international organizations, such as the World Trade Organization, Asia-Pacific Economic Cooperation (APEC) forum, etc.
In 2018, when the relations between the U. S. and Taiwan was official. This has made China was slow to improve relations with the United States, as China does not see Taiwan independent.
Learn more about American support for Taiwan from
https://brainly.com/question/1370427