Don't look to Washington.

The United States will remain the world’s most powerful nation for years to come, but the Obama administration and US lawmakers are now focused on debt, immigration, guns and growth.

A war-weary, under-employed American public wants results at home, leaving US officials to look for allies willing to share costs and risks abroad.

Unfortunately, it’s not easy to build and sustain alliances in a world where America can’t afford its traditional share of the heavy lifting.

No wonder then that the Obama administration’s greatest foreign policy successes haven’t depended on such alliances.

Withdrawing troops from Iraq and Afghanistan doesn’t require consensus among the world’s powers. President Barack Obama’s single indisputable foreign policy triumph, the killing of Osama Bin Laden, needed buy-in only from the members of Seal Team 6.

Nor should we look to Europe for help. Its leaders are still hard at work duct taping the euro zone, and cash-strapped governments consider an activist European foreign policy prohibitively expensive.

Nor will next-wave powers look to shoulder new burdens. Economic slowdowns in China, India and Brazil remind us that not every emerging market will fully emerge, much less accept the costs and risks that come with a share of global leadership.

In this G-Zero world, where no single government or alliance can lead others toward compromise, solutions to transnational problems range from ad hoc to beyond reach. United Nations Secretary-General Ban Ki-moon opened the UN’s Conference on Sustainable Development last June with a warning: This gathering is too big to fail.

But for Obama, German Chancellor Angela Merkel and British Prime Minister David Cameron, the event was simply too big to attend. None of them has the muscle, individually or together, to force compromise on the policies that fuel climate change — and they know it.

This leadership vacuum continues to expand. The risk of confrontation in Asia has grown — between China and Japan (the world’s second and third-largest economies) in the East China Sea, and between China and several Southeast Asian countries in the South China Sea.

Making matters even more dangerous, the US transition toward a sharper foreign policy focus on Asia, progress toward a massive US-led transpacific trade deal that excludes China and conflict in the under-governed expanse of cyberspace are worsening tensions between Washington and Beijing.

Fights over commercial and investment rules and the clash between the state-driven and free-market varieties of capitalism have gathered momentum. In years to come, no ties will be more important for global peace and prosperity than those that bind America and China, the world’s most powerful developed and developing states, and no development would more quickly exacerbate the G-Zero dilemma than a dramatic worsening of relations between them.

In the Middle East, Syria’s civil war grinds on with worrisome implications for neighboring countries and even Russia. Sectarian tensions are again stoking violence in Iraq. Attacks on US diplomatic targets in Libya, Egypt and Yemen have heightened Washington’s aversion to direct involvement in the region’s conflicts. This is another region in which a lack of global leadership and rivalries among local heavyweights ensure that pain will get worse before real progress can be made.

Ironically, the nation most likely to fill the leadership vacuum left by America the Vulnerable is America the Resilient. A technology-driven US energy boom has begun to create jobs, revitalize US manufacturing and offer Washington the chance to use exports of natural gas, technology and know-how to reverse the decline in US international influence.