This story is a chronicle of the legacy of slavery in the US as well as the transformations that did occur in the aftermath of emancipation, despite the continued prejudice occurring in an unequal society.
Is the story an example of a specifically American genre? I would say it is. Like the antebellum works by African American authors, it gives a picture of a dynamic that most white Americans were unaware of at the time and may still be unaware of now. In a development that might seem anomalous but in fact was not unusual at all, the story recounts that a couple who were married during the period of slavery are separated and then (possibly) reunited many years later, having become virtually unrecognizable to each other. And yet the man, Mr. Ryder, at the grand party that concludes the story, introduces the woman, Liza Jane, as "the wife of his youth."
The part of the African American experience, or the overall American experience, dramatized by the story concerns both the changed situation after slavery has ended and a subtle color barrier that existed within the African American community itself. Because he's light-skinned, in the post-bellum world, Mr. Ryder has been able to "advance" in a way Liza Jane has not. Their manner of dress, their position in society, and their speech reflect this difference. Whether Liza Jane is really the wife of Ryder's youth we are not told definitively. It could be that his own experience, one of having married young and having been separated from a woman resembling Liza Jane, is so similar to the history of her husband as she relates it that he now accepts her as his wife. Or it could be that Liza Jane really is the woman from whom he was separated, by force, decades earlier. The "Blue Veins" society of which he's a member is a status symbol for light-skinned African Americans who seem to be carrying out a prejudice of their own against darker-complected people. Mr. Ryder realizes this and wishes it were not so.
Obviously, this is not the kind of story that could have happened anywhere other than the US in the post-slavery era. It reflects the situation of married couples separated forcibly during the period of slavery and the different fates of people after the war based on nothing other than the range of skin pigmentation among them—which in itself is emblematic of the irrationality of any kind of race prejudice. Chesnutt's story is not only illustrative of a uniquely American racial history but of the "secret" history of ambiguous distinctions in "color" that have continued, unfortunately and tragically, to stymie the development of a truly equal society.