Larissa FastHorse’s comedy of performative wokeness is also a brutal satire of American mythmaking.Rehearsal rooms are embarrassing places. Actors jockey, directors bloviate, writers fume at liberties taken.We see all of that in the rehearsal room where “The Thanksgiving Play” is set, even though what’s being rehearsed is just a holiday pageant for elementary school students. Yet not just any holiday pageant. Meant to “lift up” the Native American point of view despite including no Native Americans, this one twists the drama teacher who is creating it, along with her colleagues, into pretzels of performative wokeness so mortifying they induce a perma-cringe.If that setup makes “The Thanksgiving Play,” which opened on Thursday at the Helen Hayes Theater, sound like a backstage farce akin to “Peter Pan Goes Wrong,” which opened the day before, that’s true. In both plays, everyone behaves badly, tempers flare and nothing flies right.But for Larissa FastHorse, the author of “The Thanksgiving Play,” farce is not an end in itself. Rather, it is the hilarious envelope in which she delivers a brutal satire about mythmaking, and thus, in a way, about theater itself. The stories we create can do almost as much harm as the false histories they purport to commemorate, she shows. And well-meaning people can, too.The well-meaning people in this case include Logan (Katie Finneran) and Jaxton (Scott Foley): she an imperiled high school drama teacher (her production of “The Iceman Cometh” incited parents to seek her dismissal) and he an out-of-work actor (except for a gig at the farmers market). They have mastered the buzzwords of white progressivism and use them as protective amulets, holding space for others, acknowledging privilege, sharing pronouns without being asked. Jaxton brags that he even used “they” for a year.In short, these are ridiculous figures — and yet not so ridiculous as to be unrecognizable. Nor, in Rachel Chavkin’s cheerfully cutthroat production for Second Stage Theater, are they even unlikable. Turning Logan’s anxiety into a parade of comic tics and uncertain outbursts, Finneran is endearing and even sympathetic in her attempts at righteousness, no matter how wrong they go. And though Jaxton is an obvious skeeve, decentering his maleness only as a kind of tantric come-on, Foley does it so well that the character is somehow attractive.It’s less their bad traits than their good intentions that drive you mad. Logan has engaged a wide-eyed elementary school history teacher named Caden (Chris Sullivan) to serve as a factual backstop for the pageant, then mostly ignores him. (Sullivan does puppyish disappointment beautifully.) And her casting of Alicia (D’Arcy Carden) to represent the Native American experience — under the terms of a “Native American Heritage Month Awareness Through Art Grant” — turns out to be deeply flawed. A Los Angeles actor, a third understudy for Jasmine at Disneyland and a “super-flexible” ethnic type, Alicia is not, even a little bit, Native American.Foley and Finneran’s characters, who have mastered the buzzwords of white progressivism, are ridiculous figures yet not unrecognizable.Sara Krulwich/The New York TimesNevertheless, so clever is FastHorse’s setup, and so thorough her twisting of the knife of woke logic, that Alicia, if anyone, is our hero. In part, that’s because she alone is untroubled by her whiteness — or, really, by anything. (She defends her casting by pointing out that the actor who plays Lumière in “Beauty and the Beast” is not a real candlestick either.) Still, as the team proceeds to “devise” the pageant, she’s crafty enough to steer it toward her actual strengths. “I know how to make people stare at me and not look away,” she explains (and Carden convincingly demonstrates). She’s also good at crying.In mesmerizing moments like this, FastHorse neatly sets up the tension between identity and the performance of identity — a tension she doesn’t resolve but upgrades over the course of the play to a full-scale paradox. By the time she’s finished, Logan, Jaxton and Caden are left wriggling in agony as if under a moral microscope, reduced to saying things like, “We see color but we don’t speak for it.” Eventually they conclude that the only way to center Indigenous people is to erase them.Of course, they have been erased already — repeatedly. FastHorse, a member of the Sicangu Lakota nation of South Dakota, gradually introduces the horrifying undertow of that fact with filmed segments screened briefly between the live scenes. Distressingly, these segments are based on Thanksgiving projects that real teachers have posted online. In one, adorable young children performing “The Nine Days of Thanksgiving” are made to list the many things, like “six Native teepees,” that Indians “gave” the Pilgrims. In another, fifth graders shooting turkeys with prop muskets sing a song with the lyric “One little Indian left all alone/He went out and hanged himself and then there were none.”In the play’s well-acted but somewhat diffuse premiere at Playwrights Horizons in 2018, the film sequences were less awful and violent. For Broadway, they (and the production as a whole, including its set by Riccardo Hernandez) have been pumped up to emphasize the weight of indoctrination, among adults who should know better and children who can’t. Though this is crucial to the play’s project of undoing centuries of racist mythologizing, I was left a bit queasy thinking about the young performers. Weren’t they being indoctrinated too?Filmed segments screened between live scenes are based on Thanksgiving projects that real teachers have posted online.Sara Krulwich/The New York TimesBut queasiness may be just what FastHorse is aiming for. She told the publication American Theater that she thinks a lot about “rhythm and release” in her writing. “You take your medicine, and then you get some sugar, then you take some medicine, you get some sugar.”Repeated several times over the course of 90 minutes, that cycle — enhanced by Chavkin’s pacing, which leaves you swallowing your laughter — can lead to an upset stomach. And the characters are sometimes so exaggerated for satire that they lose their grip on your emotions. Still, by the time the bloody tale of the Pequot massacre is enacted onstage, you may find yourself agreeing with Logan, of all people. Being a vegan, she already struggles with the “holiday of death”; I wanted to disown it entirely, from the turkeys all the way back to the Pilgrims.But “The Thanksgiving Play” is not primarily a brief for correcting American history. Like Tracy Letts’s “The Minutes,” which also uncovered a horrific massacre hiding in the clothing of civic pageantry, FastHorse is interested in how new information (new only to some people) might change the stories we tell in the future. The first step, to judge by the absurd crew onstage, will be to change the storytellers. FastHorse being the first Native American woman known to have a play produced on Broadway, maybe we’ve finally started.The Thanksgiving PlayThrough June 4 at the Helen Hayes Theater, Manhattan; 2st.com. Running time: 1 hour 30 minutes. More