Please don't skip the critical pieces of information:

The British and USA sent war ships to defend the KMT on Taiwan because they had been trading and negotiating junior status with the KMT and did not want the West to lose access to Chinese markets, labor, and natural resources.

The KMT immediately launched a 40-year terror campaign, called the White Terror, on the island of Taiwan and killed native Islanders as well as Han Chinese who argued that the war should be ended. The European powers funded, traded, and armed this terror.

Taiwan has been part of the nation of China for centuries. It could be argued that the distinct cultural group of native Islanders could get its own autonomous administration region, but the natives don't have much population on the island. The island has been Chinese and is inhabited by Chinese who lost the civil war and tried to secede under the protection of the Europeans, with the Europeans motivated by having a fully dependent neo-colony by prolonging the civil war and supporting the fascist terror.