In 1949, Reinhold Niebuhr published a book called “Faith and History.” Niebuhr noticed a secular religion that was especially strong in the years after World War II. It was the faith that historical forces were gradually bringing about “the unification of mankind.”

Old nationalisms would fade away, many people believed. Transportation and communications technologies would unite people. Values would converge.

This optimistic faith was at the heart of many postwar projects, first the United Nations and then the European Union. The idea was to create multilateral bodies that would hasten the process of convergence, harmonization and peace.

Unfortunately, this moral, cultural and political convergence never happened. In the decades since, people in different nations, even people within nations, have become less alike in at least as many ways as they have become more alike.

The United States is a single nation with a common history, a common currency and a strong identity. Yet the country has become more polarized, not less. The country has become more difficult to govern, not less.

As communications technology has become more global, people’s tastes have become more parochial, not less. Ethan Zuckerman of the Massachusetts Institute of Technology notes in The Wilson Quarterly that 95 percent of news consumed by American Internet users is published within the United States, and people in many other countries consume even less foreign news than we do.

The failure of convergence is most striking in Europe. True, a tiny sliver of European society is becoming more transnational. But only 2 percent of Europeans live in a different European nation than their country of citizenship.

On the whole, European nations still have very different understandings of the rule of law and political order, different work ethics and conceptions of citizenship. If you look at the European Values Study, for example, you see stark values differences across the Continent.

Less than 40 percent of Danes believe that work is a “very important” part of their lives, compared with roughly 65 percent of the French. More than 80 percent of the Croats believe that a parent’s duty is to do what’s best for their children, even at the expense of their own well-being. Only about 55 percent of Germans agree.

The world feels different depending on what nation you’re in. According to Pew Research surveys, 73 percent of Germans think that economic conditions are good right now. In France, 19 percent think that, and in Spain it’s 6 percent.

If you look at the World Values Survey, you see that people in most Western nations are becoming more distrustful of their neighbors, not less. There are huge variations across nations, but levels of social and political trust have been declining almost everywhere except the Nordic countries. If there’s convergence, in other words, it’s in our increasing agreement that we don’t trust each other.

Today’s European economic crisis grows directly out of this segmentation. The euro crisis is not a crisis of debt. Total European debt levels are not that high. It’s a crisis of legitimacy. Debt burdens are divergent across nations, and Europeans with one set of habits and values do not want to bail out Europeans with other habits and values.

The fathers of the European project believed monetary union would bring people together. But when you jam nations with diverging values together, you only end up propelling them apart.

So we face the likelihood that the euro will crack up. This is not an outcome to be desired. The ensuing recession and chaos could be horrible on both sides of the Atlantic. But we should prepare for a crackup because the underlying sense of shared identity required for the euro’s survival is not there.

Regular Europeans are losing faith in the European project. Most Europeans now believe integration has harmed their economies. In all countries except Italy, majorities oppose giving Brussels more budgetary sovereignty, according to Pew Research surveys.

The most popular major European politician is Angela Merkel, who is holding tough on more bailouts. She has 80 percent approval in Germany, 66 percent approval in Britain and 76 percent approval in France.

Europe continues to suffer from the same problem that has plagued it for the past half-millennium. There are too many nations in too small a space. There are no historical trends or technocratic schemes that are altering that basic flaw.

The larger issue is, how will the world cope with its own segmentation? How do you govern amid divergence? If multilateral organizations can’t bind nations, do we simply resort to an era of regional hegemons — or chaos?

The first step, surely, is abandoning the illusions of convergence and the schemes based upon them. In 1949, Niebuhr questioned the naïve belief that history drives toward unity. He cited the book of Psalms: “He that sitteth in the heavens shall laugh: the Lord shall have them in derision.”