For all its troubles, the U.S. economy does have one major advantage over the world's biggest industrialized nations over the next few decades: demographics. "Within four decades the U.S. will likely have one of the lowest percentages of elderly citizens, and one of the highest rates of working-age bodies among large economies," the Motley Fool points out.

(Motley Fool, the US Census Bureau)

It's largely because of America's big immigrant population: Hispanics, for instance, have a higher birth rate than average, and the influx of immigrants in the late 20th century will continue to have a major impact in the 21st. "China, meanwhile, will see its working-age population plunge and its elderly ranks soar -- an echo of its one-child policy. Europe falls deeper into age-based stagnation. Alas, Japan becomes the global equivalent of Boca Raton," the Motley Fool explains.

Joel Kotkin argues, accordingly, that Americans should fear a slowdown in immigration to the United States rather than the opposite if they truly care about the country's economic prospects.