Superpowers have always imported brainy foreigners in order to gain and maintain an advantage over other nations. The superpower does the same thing when it imports quality laborers.
However, if we leave it to the anti-immigrants to shape policy, the future of the American Superpower will be at great risk.
Some will argue that we should train and educate our own people so that they can do the work instead? While I'm very sympathetic, especially in regards to providing a quality educational opportunity to all of our children, you simply can't teach genius. Genius level intelligence is in short supply and superpowers must have a disproportionate number.
Unfortunately, the superpower's own educational system can not--and some would say, will not, produce the necessary number of highly qualified and homegrown scientists and engineers. The educational system is simply too resistant to reform. But more importantly, too many of the superpowers' people prefer to coast rather than doing the hard work of preparing for careers in leading edge fields.
In terms of laborers, a superpower has lots of people that can do the hard work, right? Well, may be not.
While superpowers grow large numbers of average working class types, increasingly many find ways to shun the heaviest and most dangerous of the superpower's work. As citizens of the superpower, domestic workers increasingly feel a certain sense of entitlement--and doing hard and low status work very well is something they reject.
The question is can a superpower survive and prosper by relying solely its large supply of Average Joes?
Honestly, the answer is no.
When Average Joes argue against immigrant workers, what they're really doing is asking for protection against workers that have more to offer the superpower in terms of intellect and work ethic. While protectionism serves the short-term interests of the Average Joes, it's against the immediate and long term interests of the superpower.