The agreement of U.S. President Donald Trump and Chinese President Xi Jingping to restart trade talks put offs planned increases of tariffs on Chinese exports. But there is little doubt that the U.S. intends to move ahead with its intention to undo the economic integration that has been underway since the 1990s. Even when it proves impossible to reverse history, the consequences of such a move will have long-lasting consequences for the global economy.

To understand what is at stake, think of the following simple guide to the status of the world’s nations in the aftermath of World War II. Countries separated into three groups, each anchored on its own tectonic plate. The “first world” consisted of the advanced economies of the U.S., Canada, the West European nations, Japan, Australia and New Zealand. These economies enjoyed rapid growth in the 1950s and 1960s, due in part to the expansion of trade amongst them. The formation of the European Community (now Union) eventually led to a single market in goods and services, capital and labor for its members. The largest of the advanced economies exerted their control through the “Group of Seven,” i.e., Canada, France, Germany, Italy, Japan, the United Kingdom and the U.S. Their leaders met periodically to discuss economic and other types of policies and issued communiques that listed their agreements. Their predominance extended to their control of the International Monetary Fund and the World Bank.

The “second world” included the Communist nations: the Soviet Union and the countries it controlled in Eastern Europe, as well as China and North Korea. These were command economies, run by government ministers. There was some commerce between the Soviet Union and its East European satellites, but all trade was managed. There were virtually no commercial or financial interactions with the first world.

Finally, there was the “third world,” consisting of the remaining nations located in Latin America, Africa, the Middle East and South and East Asia. These countries, also known as the developing economies, encompassed a wide range of economic and political models. Many of them formed an association of “nonaligned” countries that sought to preserve their political independence from the first and second worlds.

The third world had limited trade with the first world nations, and this usually consisted of commodity exports in exchange for imports of industrial goods. Import substitution, i.e., the domestic production of manufactured goods, was proposed in the 1950s as a means to counteract the disadvantageous terms of trade these nations faced for their goods. There was some migration between the first and third worlds, and there was a shift in the home countries of U.S. immigrants from Europe to Latin American and Asia. But the movements of people never approached the magnitudes of the first wave of globalization of 1870-1914.

This account is simplistic, and there are important exceptions. Yugoslavia, for example, escaped the control of the Soviet Union and had its own form of a command economy. Taiwan and South Korea began implementing export-led development policies in the 1970s. There were important differences between the capitalist economies of the U.S. and the Scandinavian nations. But the relative separation of the three “worlds” did limit their interaction, as did the political tensions between the U.S. and its allies on the one hand and the Communist governments on the other.

The partition, however, began to dissolve at the end of the 1980s as the economic tectonic plates underneath these clusters of countries began to split and move. China sought to grow its economy through the use of markets and private firms. The government promoted foreign trade, and allowed investments by foreign firms that could provide capital, technology and managerial expertise.

The dissolution of the Soviet bloc of nations was followed by the integration of the eastern European nations with the rest of Europe. Poland, Hungary, the Czech Republic and other countries provided workforces for foreign–particularly German–firms and their economies grew rapidly. The European Union expanded to include these new members, Russia itself was less successful in adapting its economy to the new configuration, and remained dependent on its oil and natural gas resources.

While the nations of the second world were moving towards those of the first world, the countries in the third world also sought to become part of the global economy. Asian nations, such as India, Indonesia, Thailand and Malaysia, adopted pro-market policies in order to accelerate development. Their expanded trade brought these countries closer to the first world. Global poverty fell, principally due to a fall in the proportion of the poor in the populations of China and India.

But there were serious disruptions to these advances, particularly in those emerging market economies that suffered financial crises: Mexico in 1995, several of the East Asian countries in 1997, Russia in 1998, and Argentina and Turkey in 2001. While some of the crises were the result of unsustainable government policies, there were also outflows of private capital that had fueled credit bubbles. The massive disruption of economic activity in the wake of these “sudden stops” necessitated outside assistance for the countries to recover. The reputation of the IMF suffered a serious blow for its slow response to the Asian crisis, and the Fund subsequently acknowledged that it had underestimated the extent and consequences of their financial fragility.

Moreover, there was collateral damage accompanying the melding of the economic tectonic plates. China’s emergence as a mega-trader had an impact on the production of manufactured goods in the U.S. and other nations. The resulting job losses, that were often conflated with those lost due to technology, turned parts of the populations of the advanced economies against globalization. Migrants were also blamed for the loss of jobs, as were global supply chains by multinational firms.

The global financial crisis of 2007-09 and the ensuing weak recovery increased the questioning of the policies of the previous two decades. Unemployment in the U.S. fell slowly, and debt crises in several European nations kept growth rates depressed. There was an acknowledgement that the benefits of globalization had not been shared equally as public awareness of income and wealth inequality increased.

There was also adverse reactions to political integration. European governments bristled against EU restrictions on their budgetary policies, while In the United Kingdom nationalists argued that EU officials in Brussels had usurped their government’s sovereignty. The waves of refugees who fled to Europe from Syria and elsewhere awakened fears of a loss of national identity.

The election of Donald Trump and the vote in the United Kingdom in favor of leaving the EU made clear the depth of the reaction against the global integration of 1990-2006. Trump’s campaign was based on a pledge to return to some past era when America had been “great,” while proponents of Brexit promised that their country would prosper outside the boundaries of the EU. The bases of support for these policies were not always wide, but they were strongly motivated.

At the same time, the Chinese government has been keen to assert its control of the country’s economic future and to resist outside interference. The Chinese also seek to establish a zone of political domination in Asia. Similarly, Russia’s President Putin has sought to set up a sphere of political and military influence around its borders. Neither government wants to cut their ties with the U.S. and other advanced economies, but they do want to maintain control over their respective geographic areas.

The China-U.S. split, therefore, is part of a larger reaction to the integration of the global economy. The removal of the barriers separating the three post-World War II “worlds” has led to anxiety and fear in those countries that were part of the first world. They look for a return to the economic dominance that they once enjoyed.

But it is not feasible to undo all the ties that have developed over recent decades, and the nations of what had been the second and third worlds will never accept subordinate status. Moreover, it is possible for the U.S. to place barriers on trade and finance that will undo the gains of the last two decades without any offsetting benefits. Even more worrisome is the possibility that economic and political divisions will exacerbate military division and result in conflict.

The earth has several geographic plates, and they move at a rate of one to two inches (three to five centimeters) per year. Over very long periods of time, the plates do collide, and the force of their movements as they smash into each other creates mountain ranges such as the Himalayas. Economic plates can move more quickly, and their collisions can be equally powerful.

We have entered into a reactionary period as self-proclaimed populists promise to segregate their countries from the outside world to achieve some form of national destiny. But it is not feasible to live in isolation, and ignoring the linkages that exist means that we are not responding to global challenges such as climate change. There may be multiple plates, but they all share one planet.