Contrary to the popular myth, immigration hasn't led to salaries in the tech sector (which has the most immigrants) to go down. In fact, in the last decade they have increased due to an increased competition and high demand.
Immigrants also lead to increased demand and job growth:
"Contrary to popular belief, immigrants do not take away jobs from American workers. Instead, they create new jobs by forming new businesses, spending their incomes on American goods and services, paying taxes and raising the productivity of U.S. businesses. Immigrants are good for the economy, not the other way around." [1]
"However, although immigrants increase the supply of labor, they also spend their wages on homes, food, TVs and other goods and services and expand domestic economic demand. This increased demand, in turn, generates more jobs to build those homes, make and sell food, and transport TVs." [2]
"Most empirical studies indicate long-term benefits for natives’ employment and wages from immigration, although some studies suggest that these gains come at the cost of short-term losses from lower wages and higher unemployment. Standard economic theory implies that while higher labor supply from immigration may initially depress wages, over time firms increase investment to restore the amount of capital per worker, which then restores wages." [2]
Immigrants also lead to increased demand and job growth:
"Contrary to popular belief, immigrants do not take away jobs from American workers. Instead, they create new jobs by forming new businesses, spending their incomes on American goods and services, paying taxes and raising the productivity of U.S. businesses. Immigrants are good for the economy, not the other way around." [1]
"However, although immigrants increase the supply of labor, they also spend their wages on homes, food, TVs and other goods and services and expand domestic economic demand. This increased demand, in turn, generates more jobs to build those homes, make and sell food, and transport TVs." [2]
"Most empirical studies indicate long-term benefits for natives’ employment and wages from immigration, although some studies suggest that these gains come at the cost of short-term losses from lower wages and higher unemployment. Standard economic theory implies that while higher labor supply from immigration may initially depress wages, over time firms increase investment to restore the amount of capital per worker, which then restores wages." [2]
[1] https://www.aclu.org/other/immigrants-and-economy [2] https://budgetmodel.wharton.upenn.edu/issues/2016/1/27/the-e...