This isn't wrong, but it never had any sort of effect on debt bondage.

Debt bondage, also known as debt slavery, bonded labour, or peonage, is the pledge of a person's services as security for the repayment for a debt or other obligation. Where the terms of the repayment are not clearly or reasonably stated, the person who holds the debt has thus some control over the laborer, whose freedom depends on the undefined debt repayment.

The problem here is that the U.S. had black codes and Jim Crow laws, things created specifically to target black people. These by and large restricted black people from owning property, marry freely, enter contracts, testify in court against white people, speaking too loudly in the presence of a white woman.

Breaking these meant that the person in question would be tried and convicted, thus entering debt. A white person could then buy this debt, and the black person would have to "work off" this debt for an indeterminate amount of time.

This was in place for a very long time, and wasn't overturned until 1941 when the office of the attorney general issued circular 3591, classifying debt peonage as slavery. They did this because the FDR administration was worried that the enemies would use the American treatment of black people against them in a propaganda war.