CNN has an opinion piece by James Goodman "It's time to stop calling slavery America's 'original sin.'"
It turns out his problem is with "original sin" as a metaphor. As I read his analysis I realized it really doesn't have that much to do with the religious doctrine. Instead it's a way of saying something really bad was done in the past, while the doctrine says humans are fated to do bad now.
Goodman makes a point towards the end, with which I do agree: the first "sin" in the creation of America was the dispossession of Native Americans.