Declining life expectancy, mass shootings, alarming rates of mental illness, rising white nationalism, the opioid crisis: By many measures, our society is in trouble, and we are ignoring a root cause: the unprecedented familial dispersion that followed the 1960s sexual revolution.

At heart, that revolution aimed to radically sever human sexuality from marriage and child-rearing, from the responsibilities society had hitherto imposed on the individual sexual appetite. Afterward, fatherless homes, family shrinkage and breakup, childlessness and abortion all became commonplace. The net effect of these changes is having fewer people to call one’s own.

Many Americans would say that their own lives have been enhanced mightily by the new liberties wrought by the ’60s revolution. Perhaps. But if we examine what these same changes have delivered at a collective level, an unsettling picture emerges.

One feature of the new landscape is widespread loneliness. And while initial studies were trained on the isolated elderly, scholarly focus is rapidly expanding as social-science data reveal ravaging isolation at the opposite end of the spectrum.

On July 30, the same day that a shooter murdered two people at a Walmart in Southaven, Miss., the latest survey by YouGov reported that 30 percent of young people in their sample of 1,254 say they “always or often” feel lonely.

Like any social phenomenon, the systemic outbreak of loneliness has more roots than one. But surely its fundamental source, for young and old alike, is the arithmetical one: the fact that more and more people now pass through life without father, sister, brother, children, cousins or varying combinations of the above — and sometimes without any of the above.

Or consider another signal development of the age that also contributes to social disunity: identity politics. In this case, too, dots connect to post-1960s kinship implosion. “The Combahee River Collective Statement,” agreed by all to be the founding document of such politics, is a manifesto acclaiming group identity as the most important source of power and protection.

It was issued in 1977, just as the first generation born after the sexual revolution came of age. It was the creation of a group of black feminists, representing a demographic cohort that was the first to experience rising and disproportionate rates of abortion and fatherlessness.

“The only people who care enough about us to work consistently for our liberation are us,” these feminists said plaintively. That statement captured a sad reality that would soon become true for many more Americans: not even having family to count on.

The fracturing of the post-1960s family and the flight to collective identities have not only been occurring at the same time. As the timeline and other evidence show, they cannot be understood apart from one another.

Identity politics is also a product of the revolution in another way. Whether one looks left or right, to politics or culture, the question, “Who am I?” has become the most frantic of our time. Traditionally, that question has been answered at least in part via primordial relations: I am a sister, a daughter, a cousin, a mother, a grandmother.

When answers that revert to family identity are more attenuated than ever before, “Who am I?” gets answered in a different way. Today’s identity communities operate as the robust family once did actually, offering members a secure place in the group, surrounding them with a simulacrum of siblings and loved ones and having their backs. But they remain shaky substitutes for the real thing.

So yes, let’s do everything we can to help our country as disparate voices urge: Reduce racism, rein in vile forms of electronic entertainment, flag potential killers, work toward a more civil order. America still won’t get better for good without a thorough diagnosis of our underlying malady.

If we are truly to recover and move on, we must begin with an honest reckoning of the impact of decades of decisions taken in the name of “choice” — whose collective deleterious effects on society are such that no single individual would have chosen them.

Mary Eberstadt is author of the new book “Primal Screams: How the Sexual Revolution Created Identity Politics.” She can be contacted at maryeberstadt.com.