It's intellectually dishonest to not compare the two.

The prison labor industry in the US is the largest, per-capita, in the world. Which makes sense, since the US imprisons more people then any other country in the world - both by capita, and by raw numbers.

There are more prisoners working for free (or nearly free) in the US today then there are prisoners in the entirety of China.

As long as the 13th amendment leaves a loophole big enough to drive a prison bus through, what you're looking at is modern-day slavery.