This is a touchy subject, and will no doubt generate plenty of agitated debate, but here goes...

Folks in the "think tank" world, as well as several high-brow magazines, are debating whether the United States' global power is shrinking. The United States will remain a major economic, military and political power for decades to come, these analysts argue, perhaps even the predominant global power. But relative to other nations and groups, its power is dimming.

In other words, the world of the lone superpower, which lasted roughly from the collapse of the Soviet Union in 1991 until now, is over.

Richard Haass, who served both President George W. Bush and his father, launches the latest salvo in this debate in an article in the new issues of Foreign Affairs magazine. Haass argues that the world is about to enter the "age of nonpolarity." This requires a quick detour into international relations theory:

* Bipolarity - That's when there are two major powers on the globe. Think Washington and Moscow in the Cold War.

* Unipolarity - One nation (and its allies) dominate. That was the post-Cold War world.

* Multipolarity - There are several or many "great powers." That describes the Colonial Era of the 19th and early 20th centuries.

In the world of "nonpolarity" that Haass describes, no one country or group is in charge. "Power is now found in many hands and in many places," he writes. U.S. power, Haass argues, is being challenged not just by rising nations like China and India, but by new power centers which are not even nations: terrorist outfits like al Qaida; nonprofits like the Gates Foundation; media outlets like al Jazeera; and inter-governmental groups like the International Monetary Fund.

This is not just Bush-bashing, although Haass says the Iraq war has contributed "to the dilution of the United States position in the world." He also faults a generation of U.S. energy policy (or lack thereof) that has left American dependent on oil imports.

Curiously, the rising power of states like China could push the United States and European Union together.

Germany's foreign minister, Frank-Walter Steinmeier, gave a speech at Harvard University on April 12 arguing for a broadened trans-Atlantic agenda that would include dealing with issues like climate change, the downsides of globalization and the resurgence of political Islam.

"No single nation can solve these problems on its own – not even the most powerful, not even the United States," Steinmeier said. His unstated message: in this uncertain world, countries that share values such as democracy need to stick together.

For another article arguing that U.S. power is in decline, click here.

Tomorrow:  An introduction to "smart power."