Not necessarily. Even in cases in which barriers exist, these barriers may be insignificant in relation to the benefits that I could realize from hiring the more productive or valuable immigrant over the less productive or valuable American. In a free society, I should be free to hire anyone regardless of his nationality, at least as long as that person is here legally.
It would also tell you that trust and security are greater with your countrymen than with new immigrants.
Not necessarily. It depends on the moral character of the individuals involved. I'm better off hiring an immigrant of high moral character over an American of low moral character.
If you don't have even a basic loyalty or concern for your country, your rational self-interest would tell you to run fast, because the angry mobs of exploited workers are coming to burn down your immigration import house.
Maybe in the Nazi Germany of the 1930s, but not in the United States -- at least not yet. In this country, we should have the freedom to employ the best person for the job, regardless of nationality.