Americans are not scared about unregulated immigration because it does not reduce job opportunities for native born Americans or leads to increased unemployment. Many immigrants are typically come relatively poor, and take on menial labour tasks that native American citizens are unwilling to do. This fills key gaps in the country's economy and their contributions would be difficult to replace if there was mass deportation.
In the long run, evidence suggests that immigration actually raises national income and output, and contributes to maintaining a dynamic and growing society.
Immigrants also increase America's national birth rate, helping to offset the ageing population. This reduces any decline in the labor force and counteracts slow economic growth.