The examples go on and on.
Where forced labor still exists there is something else propping it up or subsidizing it - like I mentioned with prison labor.
I'm also dubious of your Kansas claims (Google search comes up with nothing). Again, by the same standard, I can claim that the US "cannot even clothe itself" today. I'm sure reality is a lot more nuanced than that.
I can expand further on history of the USSR and long-term effects of WW2 on that country's population, which had massive waves of effect well into 1990s, but I'll stop here.
citation needed
As for prison labor, most of the cost of that is borne by the taxpayer, not the company using their labor. Keeping people prisoners in the US is very expensive.
1) The Civil War was absolutely about slavery. Here's a professor at West Point talking about: https://youtu.be/pcy7qV-BGF4 (and PragerU is a very conservative source too).
2) The Emancipation Proclamation didn't end slavery. It ended it in states that were still rebelling. It took amendments to the Constitution to end slavery once and for all.
3) I agree that keeping prisoners is very expensive in the US and that most of that cost falls on the taxpayer. But it is very much still (essentially) slavery that the "free market" uses.
Actually, it ended because it could not compete with free labor. It was dying around 1800 because of that, and then the cotton gin revived it. It was dying again in the 1850s, and a big driver of the Civil War was the slave states trying to protect their economy from free labor competition.
I don't think it's a coincidence that social justice has tended to follow what works best economically.