If you buy into economic theory wages are what they should be given the supply and demand curves which impact wages. Wages are not cheap or expensive... they are what they are given the market.
When there is strong demand wages go up, when there is an excess of labor wages go down.
Unions "distort" the market upwards. Bringing in legal and illegal immigrants increases supply and therefore puts downward pressures on wages. Wages are a reflection of market forces and govt policies. ( I will address slave labor in a moment.)
So saying "America was built on cheap labor" is ignorant of economic theory and/or pregnant with leftist propaganda.
A more reasonable comment would be to say the Southern economy was highly impacted by slave labor for a period of time.
In my view, you and those many who would agree with you, have not correctly analyzed labor. I.E., in actual practice, the wages of low-wage labor may not directly reflect market forces, and may not rise with invention and capital accumulation as Smith had envisioned.. For a classical Adam Smith supply/demand market, i.e., one that meets his criteria as described in "Wealth of Nations,"
Both Demand
and Supply sides must approximate elastic* behavior. Republican policies have precluded an elastic supply side, i.e, when wages too low to live on are offered by the Demand side, the supply does not dry up as it should according to a classical Supply and Demand market. The reason is quite simple to understand. In the U.S., a third party is involved. The third party is the Government, or a spouse, or parents. The current market for low wage labor in no way approximates a classical, two-sided, supply and demand market as envisioned in textbooks. This is the result of low wage labor being subsidized. Were it not, in a classical supply/demand market, wages would have to rise because supply would decline. This is not at all what Adam Smith had in mind . It is also likely that Smith did not anticipate rising productivity coupled with a declining demand for labor, another important factor leading to deviation from classical behavior.
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*A term not used by Smith, so far as I am aware, but much used by modern economists.