These days, it’s impossible to think about America and its future role in the world without also thinking about China. This was the subject of a combative discussion last week at the Aspen Ideas Festival.

The agent provocateur was Niall Ferguson of Harvard. China and the United States, he argued, used to have a symbiotic relationship and formed a tightly integrated unit that he calls Chimerica.

In this unit, China did the making, and the United States did the buying. China did the saving, while America did the spending. Between 1995 and 2005, the U.S. savings rate declined from about 5 percent to zero, while the Chinese savings rate rose from 30 percent to nearly 45 percent.

This savings diversion allowed the Chinese to plow huge amounts of capital into the United States and dollar-denominated assets. Cheap Chinese labor kept American inflation low. Chinese efforts to keep the renminbi from appreciating against the dollar kept our currency strong and allowed us to borrow at low interest rates.

During the first few years of the 21st century, Chimerica worked great. This unit accounted for about a quarter of the world’s GDP and for about half of global growth. But a marriage in which one partner does all the saving and the other partner does all the spending is not going to last.

The frictions are building and will lead to divorce, conflict and potential catastrophe. China, Ferguson argued, is now decoupling from the United States. Chinese business leaders assume that American consumers will never again go on a spending binge. The Chinese are developing an economy that relies more on internal consumption.

Chinese officials are also aware that America will never get its fiscal house in order. There may be theoretical plans to reduce the federal deficit and the national debt, but there is no politically practical way to get there. Depreciation is inevitable, and the Chinese are working to end the dollar’s role as the world’s reserve currency.

Chinese nationalism is also on the rise. The Internet has made young Chinese more nationalistic. The Chinese are acquiring resources all around the world and with them, willy-nilly, an overseas empire that threatens U.S. interests. The Chinese are building their navy, a historic precursor to expanded ambitions and global conflict.

Think of China, Ferguson concluded, as Kaiser Wilhelm’s Germany in the years before World War I: a growing, aggressive, nationalistic power whose ambitions will tear through pre-existing commercial ties and historic friendships.

James Fallows of The Atlantic has lived in China for the past three years. He agreed with parts of Ferguson’s take on the economic fundamentals, but seemed to regard Ferguson’s analysis of the Chinese psychology as airy-fairy academic theorizing.

At one point, while Fallows was defending Chinese intentions, Ferguson shot back: “You’ve been in China too long.” Fallows responded that there must be a happy medium between being in China too long and being in China too little.

Fallows pointed out that there is no one thing called “China” or “the Chinese,” and that many of the most anti-American statements from Chinese officials are made to blunt domestic anxiety and make further integration possible. That integration, Fallows continued, is deep and will get deeper. Many, many Chinese leaders were educated in the United States and admire or at least respect it. If you go to cities like Xian, you find American and European aviation firms fully integrated into the commercial fabric there.

Fallows’ main argument, though, was psychological. When he lived in Japan in the 1980s, he said, he sometimes felt that the Japanese had a chip-on-their-shoulder attitude in which their success was bound to U.S. decline. He says he rarely got that feeling in China.

Instead, he has described officials who are thrilled to be integrated in the world. Their mothers had bound feet. They themselves plowed the fields in the Cultural Revolution. Now they get to join the world.

Some of the officials interviewed by Fallows believe that the United States is following unsustainable fiscal policies that will lead to decline, but they view this with frustration, not joy. Fallows doesn’t know what the future will hold, but he believes that Chinese officials still see the dollar as their least risky investment. Domestically, China will not turn democratic, but individual liberties will expand. He agreed that China and the U.S. will dominate the 21st century, but he painted the picture of a more benign cooperation.

I came to the debate agreeing more with Fallows and left the same way, but I was impressed by how powerfully Ferguson made his case. And I was struck by their agreement about what to do. This conversation, like many conversations these days, gets back to America’s debt. Until the United States gets its fiscal house in order, relations with countries like China will be fundamentally insecure.