"I don't think the bulk of manufacturing that left did so for reasons other than cheaper labor or lower environmental protection translating to greater margins. If thins were as bad as you'd say they'd move the whole operation overseas, not just the low-skilled high-polluting labor-intensive parts."
First, the purshase pf labor is no different, and completely related to the purchase of consumer goods. Lower labor/supply costs means greater flexibility and greater competition, which results in lower prices for consumers. Employers seek the cheapest labor for the same reason that shopper seek low cost stores like Wal Mart. Because it allows them to do more with a set amount of income. And firms are responsive to consumer needs. If consumers want to spend more for american made goods, they are still free to do so. Most would rather not, and retain the money they would have otherwise spent.
Second, manufacturing really took off in the US because this country had the only stable industrial base during WWII. The Germans were very good at it, and had they leveraged it for more peaceful purposes, they might have ended up ruling the world. By invitation. But they didn't. They started a war, and the US became the main supplier of allied military hardware. Afterwards, they continued to be the largest producer because they were the last industrialized country left standing. As Europe and Asia rebuilt, competition increased, and reduced demand for American made goods. This in turn resulted in a reduced demand for the unskilled labor that was vital to industry.
I'm pretty sure I have taught you this before.
"If you can't bring in enough revenue to pay your workers enough to live, your business model has a fatal flaw."
An entprise doesn't exist to provide jobs for people. It exists to provide for the needs of the consumer. The more consumers are forced to pay, the less incentive there is to purchase those goods or services, especially those that are price elastic.
"The business model relies on the government assistance to keep those employees alive and showing up for work. There is no getting around it."
But what happens if you double labor costs to provide a living wage. Increased costs are going to mean that employers are going to have to charge more, cut quality, or reduce the number of employees. So a business that previously employed 20 people would rationally reduce the number of employees and replace them with improved processes or technology. If they can't do that-if they have to cut qusality or increase prices, the result is going to be a reduciton in demand. Again leading to a decrease in demand for labor.
There's really no getting around this without introducing centralized government planning where consumer choices and employer practices are determined and regulated by a government agency. Kinda like the USSR. Marx knew this to be the case. Lenin certainly did.