When did the United States ban immigration?

It will not be banned, because regular immigrants will bring a lot of income, and the United States now has a population of 300 million, which will only become more and more formal and the number of immigrants will be limited. After all, the total population should not be allowed to grow too fast, and the number of immigrants will decline when the economy remains unchanged. At present, most developed countries are under-populated and attract high-quality immigrants.