How did immigration to the united states in the last two decades of the twentieth century and the first decade of the twenty-first benefit the american economy but produce political backlash?

The million arrivals of immigrants in the early 20th century spur economic growth because low skilled labor was needed for the manufacturing industries and was not available locally, and highly skilled arrivals were source of innovations and inventions.there was however a major political back lash against the immigrants which led to the emergence of nativists.

Very useful. it is to learn because history repeats itself so learning about it those mistakes not happen again.