By the time of the formation of the USA indentures were no longer being allowed. Also indentures were for a limited time (7 years max I think), and not renewable. Things like "selling" children in to serfdom/indenture would not be legal. Furthermore I doubt that after the cessation of the importation of African slaves (1809), using this as a dodge to import more "slaves" would not be acceptable to any but the states of the deep south (not even the states of the upper south would go for this).
White masters/overseers using black women was OK (sort of). The problem is white serfs, who are white skinned which is what counts, having even informal slave marriages with black women. Even worse, if any of the female serfs are white (or passable white children from white/ mulatto slave relationships), them having any sex with black men especially consensual, is waaaay over the line.
Not all of the whites in the south were pale/freckled Irish. Descendants of French and Spanish origin folks (Florida, Louisiana, parts of Mississippi and Alabama in particular) are Mediterranean in skin tone.
White masters/overseers using black women was OK (sort of). The problem is white serfs, who are white skinned which is what counts, having even informal slave marriages with black women. Even worse, if any of the female serfs are white (or passable white children from white/ mulatto slave relationships), them having any sex with black men especially consensual, is waaaay over the line.
Not all of the whites in the south were pale/freckled Irish. Descendants of French and Spanish origin folks (Florida, Louisiana, parts of Mississippi and Alabama in particular) are Mediterranean in skin tone.