The truth, though, is that Fitzgerald was right and practically everyone who quotes him is completely missing the point. How plausible is it, really, that one of the great minds of Western literature couldn't comprehend of a singer who acts or a politician overcoming a corruption scandal? Moreover, this particular author wrote The Great Gatsby, the definitive novel of American self-invention, in which the title character utterly remakes his identity to fit the "Platonic conception of himself." The idea that Fitzgerald, of all people, didn't believe Americans could reinvent themselves is a like thinking Tolstoy didn't believe in snow.
The misconception comes from a lack of context—or maybe deficient math skills. People who quote the line seem under the impression that most theatrical plays have two acts. If that were so, "no second acts" would indeed mean what's it so often mistaken to mean. Something like, "American lives are one-act plays." Or, more broadly, "Americans live hard and die young," a sentiment in keeping with Fitzgerald's own reputation for fast-living and his love for characters that are young, rich, and doomed. Even then, you could make a case that he's right—using examples of iconic "one-act" American lives from to James Dean and Marilyn Monroe, to Jimi Hendrix and Kurt Cobain.
The problem, though, is that most stage plays don't have two acts. Traditionally, they have at least three—a fact of which Fitzgerald, who wrote for the theater at Princeton and later Broadway, was well aware. With "no second acts," he was almost certainly referring to a traditional, three-act drama, in which Act I is establishes the major conflict, Act II introduces complications, and Act III is for the climax and resolution. "No second acts," therefore, means Americans skip from Act I to Act III. That is, we are frustrated by stories that go too slowly, especially due to obstacles that are alien to our national character.
The class conflicts that drive British manners comedy, for instance, can feel pointless to Americans, who consider upward mobility a birthright. Russian drama, with its tragic fatalism, seems foreign to a nation founded on individualism and self-reliance. Americans like stories with sharp moral distinctions and lots of action; stories where individuals make decisive choices to bring about a clear resolution—typically the happy ending. Something along the lines of, "Americans stories should cut to the chase" is much closer to what Fitzgerald was trying to say—a claim Hollywood has proved dazzlingly correct.
Whatever he meant precisely, though, it clearly had nothing to do with Darius Rucker's switch from rock to country. The author wasn't saying anything as silly as "There are no comebacks in American lives" or that we don't believe in second chances, as those who quote the line imply. On the contrary. If anything, an American penchant for skipping the second act and jumping to the resolution speaks to how much we love a comeback—and how impatient we are to see a character redeemed.