> Different workers in different nations have different cultures and compete with each other for a scarce supply of buyers.

This is a description of the status quo of capitalist competition, but is not a fact of nature. We can arrange our economies to work in cooperation with one another, rather than in competition. Competition is used specifically to depress all worker wages for the benefit of the ownership class, and we do not have to accept that at face value.

well, the unions pushed for wage requirements in the auto industry within the USMCA (NAFTA2) and required Mexico to (effective) legalize unions alongside lots of other rights enshrining measures. So Mexican workers benefited greatly from the work of these unions.