This kind of intense localism may lead one to befriend unfamiliar neighbors, and hospitality is a major theme of Mr. Dreher’s book. But at a time when many Americans live in economically and ethnically segregated communities, it seems doubtful that further withdrawal from the world will stimulate radical empathy. The urge to batten down the hatches may actually feed the cultural patterns that enabled the election of Donald Trump: the impulse to associate only with people like ourselves and grow even more certain that evil forces are persecuting us.

Luma Simms likes to say that she tried the Benedict Option before it was trendy. She emigrated to California from Iraq as a young girl. Her father was Syrian Orthodox, her mother a Chaldean Catholic, but the desire to assimilate drove her to convert to evangelical Protestantism. “When I asked myself, what does it mean to become American, part of the answer was espousing an evangelical Protestant worldview,” she told me. “I wanted to be on the political side that believed America was good.”

After Ms. Simms became a parent, she began to worry about the influence of secular culture on her children as well as the politicization of mainstream evangelicalism. In 2006 her family moved to Arizona to join an insular church that promoted home schooling and strict patriarchal authority. “We were protecting our children, raising them up to be stronger citizens of a rightly understood America, so that when American culture starts collapsing like Dreher keeps telling us it will, they would rise up, having been well disciplined and educated, to become leaders,” she said.

The community was so cloistered and dogmatic that it estranged her from her oldest daughter and pushed her to cut off contact with her own parents. The church “made families like us view almost everyone outside that circle as a potential enemy of our thoughts,” Ms. Simms told me. After a dispute over the pastor’s authority, the church disintegrated in 2010.

Even mainstream churches can inadvertently encourage this kind of cultural quarantine: Most Americans still bow their heads in congregations dominated by a single racial or ethnic group. Although the diversity of congregations is growing nationwide, eight in 10 Americans still attend a house of worship in which one ethnic group makes up at least 80 percent of the congregation, according to the most recent National Congregations Study.

Reformers have long been working to build multiracial bridges in Christian academia and media, but these efforts alone won’t desegregate religious fellowship. Ekemini Uwan is a Nigerian-American who has ventured farther than most black Christians into the citadels of white evangelicalism. Last year she graduated from Westminster Theological Seminary in Glenside, Pa. For most of her time there, she was the only black woman in her program, she told me (the school has a sizable Asian student population, but fewer than 6 percent of students identify as black or Latino). She writes for traditionally white evangelical media, like Christianity Today magazine. But she has continued to attend “a predominantly black church” in Philadelphia, she said.