The immigrations into the USA before, during and after the 19. century caused fundamental changes of the country.
Originally, some British Immigrants, also known as " Pilgrim Fathers ", had begun to populate American land in the 17. Century. They built colonies and spoke widespread English so that the American motherlanguage is a consequence of these settlements.
Later, outcasts from Europe came to it and rich plantation owners called over 400.000 African slaves their own.
This historical process is the trigger of the eternal Black-White conflict, because the originally reason for bringing Africans to America was that they have to serve as slaves for obtaining much money.
Furthermore, in the 19. century lots of other Europeans like German, Sweden, Irishmans and Norwegians but also Asian people immigrated. They all brought their own traditions, customs, religions, skills and cultures into the USA and so the currently society were built.
During the last century, millions of Immigrants came annually and also many Jews from begin of the Nazi-regime.
For summing up and making the point you can say that the immigrations had produced a multiculture society, which united a completely different-thinking nation...