The idea that international socialists have that domestic labor conditions are made worse by a lack of protections for foreign workers (rather than the presence of the workers themselves) doesn’t pan out if you look at Canada; it’s quite rare for status in the country to be tied to a particular employment agreement, so immigrants are free to leave undesirable employers, but wages are substantially lower there due to the country having accepted about 3 million immigrants and temporary workers in the span of the last ten years.