Why can Americans move to Taiwan Province province, while mainlanders can't?

The United States does not need a visa to go abroad. Ordinary people can think that if they want to go abroad, most rich people in the United States will return home. It is basically difficult to go to that country at home, because the poor government in China is afraid that ordinary people will never come back after going abroad. In fact, it is possible to go to Taiwan Province Province, but it is extremely difficult to go through the formalities.