The United States does not restrict fertility, and there are a large number of immigrants every year. Why is the population growth slow and controlled so well? Waiting for an explanation

The welfare in America is very good. It is reported that there is a beggar who does nothing, has good hands and feet, and receives petty-bourgeois relief every month. In China, raising children is mainly for providing for the elderly. In America, no one will worry about this problem. The service in the nursing home is simply too good to imagine. Besides, the United States has only been open for hundreds of years, and the west is still desolate. We have lived for thousands of years, and people are everywhere. There is a lot of land, so the house price is low, but one disadvantage is that kindergartens in the United States are criticized, accidents often occur, and even children in custody die unexpectedly.