You're moving the goalposts.

Your comment stated: "And does Brazil have their own 13th amendment that allows them to use prison labor as their modern slave workforce?"

The article I linked states: "Most countries’ legal systems, however, carve out an exception for prisoner-workers, permitting the state to require them to work..."

So my quote directly answers your original concern.

Your new concern is about private prisons. Here's a new quote from the article which addresses your new concern:

"Involvement by non-public entities in prison work can take many forms. In most countries including all three of Brazil, the United Kingdom, and the United States, for-profit companies operate entire prisons (or provide services within prisons) under government contract. Similarly, the operators of both public and private prisons in all three countries contract with buyers, equipping prison workshops and using prisoner labour to produce goods and services which go on to be sold beyond the prison."

(p. 15, emphasis mine)

So no, the US system doesn't seem to be especially unusual, according to this article.

You're welcome to decry this practice as inhumane, btw. I just don't think it is some sort of skeleton key which will help us understand every aspect of US politics.