Amy Chua is an uncomfortable presence in American intellectual life. In both her important scholarly works and her candid personal writing, Chua approaches the no-go areas around which others usually tiptoe. The warning alarms burst into “WAH-OH, WAH-OH” — and Chua greets the custodians with a mild, “Oh sorry, was that a taboo?”

“Political Tribes,” the newest book from this unconventional writer, is haunted by the events of 2016. Chua’s message: Ethnocultural rivalry powerfully shapes both international relations and domestic policy. Ethnocultural rivalry will not be reasoned away. Its divisions are hard-wired into the human brain. The American reluctance to recognize this truth, Chua continues, derives from the country’s own unique inheritance, which optimistically insists that the nation’s internal divisions can and must be melted down into a shared ideology of Americanism. That inheritance, she argues, blinds Americans to the world around them — and even more ominously, deceives them about the most important trends within their own society.

“For 200 years,” Chua writes, “whites in America represented an undisputed politically, economically and culturally dominant majority. When a political tribe is so overwhelmingly dominant, it can persecute with impunity, but it can also be more generous. It can afford to be more universalist, more enlightened, more inclusive, like the WASP elites of the 1960s who opened up the Ivy League colleges to more Jews, blacks and other minorities — in part because it seemed like the right thing to do.

“Today, no group in America feels comfortably dominant. Every group feels attacked, pitted against other groups not just for jobs and spoils but for the right to define the nation’s identity. In these conditions, democracy devolves into zero-sum group competition — pure political tribalism.”

Chua professes no concern that America will be swept by outright white nationalism. But she does perceive that “a kind of ‘ethnonationalism lite’ is widespread among white Americans today. It does not dream of an all-white America; it opposes racism and celebrates tolerance and exults in the image of America as a ‘nation of immigrants.’ But it is nostalgic for a time when minorities were not so loud, so demanding, so numerous — a time when minorities were more grateful.”

Chua sees this, does not like it and hopes something can be done about it. She takes comfort from local efforts like a project in Utica, N.Y., where Bosnian Muslim immigrants and local Unitarian Christians watched a Super Bowl together. She applauds aggressive racial integration programs like those run by the American military. She cites her own teaching experience in small seminars at Yale, where students from divergent backgrounds overcame disagreements to achieve mutual respect, sometimes even friendship.

Yet the scholar in Chua acknowledges that these individual experiences offer less of a social lesson than she would wish.

“Studies show that minimal or superficial exposure to out-group members can actually worsen group division. … Negative interactions with people from other groups also increase group hostility. So merely putting members of different groups in the same space is not enough and indeed can aggravate political tribalism.”

In the end, Chua falls back on the very attitude to which she turned her sharply skeptical gaze at the beginning of the book: the conviction that the United States was, is and will remain an exceptional nation, different from all the others. In her introduction, Chua remarked that the United States as a supertribal entity indifferent to ethnicity and culture became at best a partial reality only a generation ago. By book’s end, however, the battered ideal has been polished and refurbished.

“With every wave of immigration in the past, American freedom and openness have triumphed. Will we, telling ourselves ‘These immigrants are different,’ be the weak link, the first generation to fail? Will we forget who we are?” That’s inspiring, and even more so are the citations of Martin Luther King Jr., Lin-Manuel Miranda and Langston Hughes that finish the book.

Inspiring — but not wholly reassuring. A lot of the interest of “Political Tribes” comes from the strong sense it emanates of an author arguing with herself. Chua both condemns tribalism and respects its power. She insists that the United States alone of nations among the earth has often transcended it — and then presents impressive contrary evidence from the past and the present. Chua reckons with the many tribalisms of the American past: ethnic, religious and racial. She hopes for a future in which tribalism fades — even as she mercilessly details its accumulating strength.

As Chua notes, tribes can coalesce out of previously unrelated pieces. Immigrants to Europe from North Africa, the Middle East and South Asia — of different languages, ethnicities, folkways and religious practices — raised children who created for themselves a new identity as post-ethnic Muslims. ISIS, as Chua mordantly observes, is in its own way a melting pot, bringing together young men and women from across Europe, Asia and the Americas to fight for a new ideology. She quotes a New York Times article about young British girls lured to ISIS. For them, “Islam is punk rock.”

Tribes can be created by fission as well as by fusion. Chua suggests that in the United States, divisions that would once have been understood as class divides have been reinterpreted in our time as cultural, even when they are not ethnic. “White Americans often hold their biggest disdain for other white Americans — the ones on the opposite side of the cultural divide.”

These fast-evolving and ever-changing identities may look contingent from the outside. They feel overwhelmingly powerful to those inside. Chua repeatedly scolds American policymakers for underestimating the importance of ethnocultural identity in Vietnam in the 1960s, Venezuela in the 1990s and Afghanistan in the 2000s. Through her book pulses an evident worry that tribal claims are now overpowering national ones within the United States. If she cannot quite bring herself to make her own anxieties explicit — or figure out what if anything to do to address them — she is hardly alone. As the rise of Donald Trump over more conventional politicians has so emphatically proved: Worsening social divisions are much easier to exploit than to explain or redress.