I'm struggling to follow what immigration has to do with discrimination against US-born individuals. Is the connection because, without the broader pool of applicants available through visa programs, companies would be forced to hire an increased amount of US-born people who wouldn't otherwise have been hired, some of whom would have been potentially not hired due to discrimination? If anything, my discrimination meter would go in the other direction, that when a company explicitly doesn't sponsor any visas, they would be discriminating against non-US-born individuals.