Overall, immigration has been shown to be beneficial to the American economy.
The first huge wave of illegal immigrants, the white European settlers that swept across North America, brought epidemic diseases, nearly exterminated the bison, completely exterminated passenger pigeons, and due to overgrazing, turned certain areas of the west into deserts. However, this group of immigrants was responsible for the industrialization of the area and for dramatic GDP growth.
Subsequent waves of immigration have led to increased ethnic diversity and population growth. Immigrants, despite having a lower average income in the first few generations than citizens, pay more in taxes than they receive in services. They often take difficult and strenuous jobs in industries such as agriculture, meat-packing, and domestic service that most citizens refuse to do. As well, immigrants tend to be highly entrepreneurial, and are per capita responsible for starting more new business than U.S. citizens. Guest workers, especially in STEM (science, technology, engineering, and mathematics) fields, fill jobs in areas where there are more job openings than there are qualified workers.
One major economic criticism of United States immigration policy is that its family preference is less economically beneficial than the Australian and Canadian skill preference model. Currently, the United States turns away doctors, computer programmers, and people with PhDs in engineering in favor of uneducated family members of existing citizens, a policy that is not economically ideal.