What are the different reasons why people from Europe, Africa and Asia immigrate to the United States?

Africans were sold to the United States after being colonized, but some unyielding blacks escaped. As a result, millions of escaped blacks died. Asians were tricked into building railways in America, and many people died. However, those who survived and repaired the railway were the first to get green cards there. Europeans colonized everywhere at that time, and they came to America for their own benefit.