Are you saying that an employer has hired illegal workers causing legal workers, who are unable or unwilling to work for the same low wages, to be out of work?
There are, of course, requirements for employers to verify the immigration status of all employees before they hire them and employers have been fined and jailed for hiring illegal immigrants (as discussed here). Any kind of suspicion that an employer may be hiring illegal workers can be reported to the U.S. Immigration and Customs Enforcement at the number indicated here.
However, an employee, unless an employee has a written employment contract or a union contract, is normally considered an "employee-at-will," and employers can hire or fire an employee-at-will at any time, for any reason, or for no reason at all (except where there is discrimination or other illegal activity). Discrimination may be said to occur where an employer fires a US citizen to hire non-US citizens (this is an idea, not a proven matter), because discrimination due to national origin is illegal. But, again, that is only a potential legal theory, a possibility.
You may want to consider speaking to an attorney (often, many initial consultations are free), perhaps one who works in employment law, to review your situation to see if you may have any claims against a former employer given your situation.
DISCLAIMER: Answers from Experts on JustAnswer are not substitutes for the advice of an attorney. JustAnswer is a public forum and questions and responses are not private or confidential or protected by the attorney-client privilege. The Expert above is not your attorney, and the response above is not legal advice. You should not read this response to propose specific action or address specific circumstances, but only to give you a sense of general principles of law that might affect the situation you describe. Application of these general principles to particular circumstances must be done by a lawyer who has spoken with you in confidence, learned all relevant information, and explored various options. Before acting on these general principles, you should hire a lawyer licensed to practice law in the jurisdiction to which your question pertains.
The responses above are from individual Experts, not JustAnswer. The site and services are provided “as is”. To view the verified credential of an Expert, click on the “Verified” symbol in the Expert’s profile. This site is not for emergency questions which should be directed immediately by telephone or in-person to qualified professionals. Please carefully read the Terms of Service (last updated February 8, 2012).