Reasons why Asia, Africa and Europe immigrated to the United States.

1, the core reason of European immigration is that the collapse of feudal system in Europe led to a large number of bankruptcies of farmers and craftsmen.

2. The reason for African migration is the sharp decline of Native Americans, and a large number of European slave traders sell slaves from Africa to America.

3. The reasons for Asian immigration are similar to those in Europe, both of which are the bankruptcy of feudal natural economy.