Western workers relative prosperity relies on the exclusion of workers from poorer countries. Although myth greatly exaggerates the prosperity of American workers during the so called American Golden Age of 1948 to 1973. In relative terms American prosperity was at its height in this period and it depended not only on labour immobility, but also capital immobility. The prosperity of the mass of a country's population at its crudest relies depends on two variables, the average level of productivity and the supply / demand balance of Labour to Capital.
American workers in this Golden Age had a vast amount of captive capital. Both Capital and Labour were relatively immobile. Globalisation has allowed the Capital to move to the (cheap) Labour and the (cheap) Labour to move to the Capital. What the left won't admit is that Globalisation has been an enormous, enormous benefit to non White people. Non White people have benefited enormously from globalisation both by being able to leave their shit hole (to use the technical academic economic terminology) countries in unprecedented numbers and have the great opportunities of western countries. But also many under developed countries have been transformed, though access to western capital, western markets, western technology and western culture.