@Baldimo,
They're not taking jobs away from Americans. The demand for engineers in Silicon Valley is at its height. Simply put, demand is higher than supply. The only way the high tech companies can continue to expand is to get our government to expand its green card immigration permits to hire the best from outside the US. That's how our country remains competitive in the world marketplace.
Even Engineering PhD's earned at US colleges and universities are by foreign students. It behooves our high tech companies to hire them - as many as possible.
On the lower end of the job scale are service industries. Not many Americans are willing to wash dishes, wait on tables, or work as a bus boy. Many from other countries love nothing better than to come to the US to fill those jobs.
It's the same as on cruise ships; most of the workers are from foreign countries, and not many Americans are found working as stewards, waiters, cooks, maintenance workers, servers, and the majority of service jobs.
Without those workers from foreign countries, cruise ships wouldn't be providing this service.