Also many foreigners on visas working in United States don't have to pay FICA Social Security tax. Do you think they would have an advantage over Americans for hiring employers when the employers don't have to match 7% of their salary into FICA? You bet it does.
To add insult injury they're not subject to the 7 1/2% withholding taxes American citizens are.
Here's a summation of how this works.
Do nonresident aliens have to pay FICA tax?
If you're a nonresident in the US you may be exempt from Social Security and Medicare taxes (FICA).
International students, scholars, teachers, professors, researchers, trainees, physicians, au pairs, summer camp workers, and other non-students on F-1, J-1, M-1, Q-1 or Q-2 visas are entitled to a FICA exemption.
Source https://blog.sprintax.com/fica-tax-explained-nonresidents/
take a look at the other tax-preferred elephant in the room: The OPT visa.