From a historical perspective, why do people immigrate to the United States?

With the opening of new air routes, the upsurge of emigration to the United States has gradually taken shape. The discovery of the American continent provides a new environment for residents who have difficulties in living in Europe. The reason why people choose to immigrate to the United States on a large scale is related to the different historical environment of the immigrant class. For example, immigrants from western Europe, because of their strong advocacy and the constant wars in Europe, make it difficult for people to survive, so they choose to seek new opportunities on the other side of the ocean. Italy emigrated because of poverty and internal strife. Immigrants from Asia are either kidnapped or actively pursued. Most of them hope to change the unfavorable situation in their country. African migration is basically caused by the slave trade. This is inseparable from the dirty activities of the British.