Who drives the bus?

IS THE US really in decline? Can China become a superpower? Can Europe rebuild? How fast can the rest rise?

These are interesting issues, but today's world faces a more urgent and important question: While we're figuring all that out, who will lead? Unfortunately, the answer is no one. In this G-Zero era, no one is driving the bus.

The United States and its European allies can no longer drive the global political and economic agenda.

The scramble to produce a coordinated and effective multinational response to the 2008 financial crisis made that clear, but the growing leverage of emerging states like China, India, Brazil, Russia and others was apparent years before US financial institutions began melting down and the Eurozone descended into crisis.

Yes, America remains the most powerful and influential country on Earth - and will for the foreseeable future. Its economy is still the world's largest. No single nation can compete with its cultural influence, and only America can project military power in every region.

But in coming years mounting federal debt and the domestic political attention now focused on this issue will force the architects of US foreign policy to become more sensitive to costs and risks when making potentially expensive strategic choices.

At home, it will be harder for presidents to persuade taxpayers and lawmakers that bolstering the stability of countries like Iraq or Afghanistan is worth a bloody, costly fight. That means decoupling support for a "strong military", an always popular position, from security guarantees for countries that no longer meet a narrowing definition of vital US interests.

Abroad, questions will arise about America's commitment to the security of particular regions, encouraging local players to test US resolve and to exploit any weakness they think they've found. Few want a global policeman, but some will have second thoughts when they realise they lack protection against a neighbourhood bully.

Yet, other countries aren't exactly lining up to fill this vacuum. The ongoing battle to bolster the eurozone will discourage European leaders from searching abroad for new ways to extend the influence of their governments, and leading developing states have too many challenges at home and foreign-policy plans for their immediate neighbourhoods to embrace the risks and burdens that come with a larger share of global leadership.

China's leaders, in particular, already have their hands full. They have already acknowledged that their country's growth model is "unstable, unbalanced, uncoordinated and unsustainable", and they know that their ability to guide the country through the next stage of its development is far from certain.

India, Brazil, and Turkey can continue to grow for the next 10 years with the same basic formula that triggered growth during the past 10. The United States, Europe, and Japan can reinvest in economic systems that have a long history of success. But China must undertake enormously complex and ambitious political and economic reforms if it is to continue its drive to become a modern, middle-class power.

China faces the added complication that today's international environment is fast becoming less friendly to China's expansion.

Higher prices for the oil, gas, metals and minerals needed to fuel China's expansion will weigh on growth.

The rise of other emerging powers will add to the upward pressure on food and other commodity prices, undermining public confidence in government, the most important source of China's social stability. In addition, as state-backed Chinese companies draw their government into the political and economic lives of so many other countries, they face the same backlash from local companies and workers that plagues so many other foreign firms doing business far from home.

And because the Chinese government has such a direct stake in the success of these companies, Beijing will be drawn into conflicts it has never coped with before.

We can't know what the future holds for the United States, China, or any of these countries. There are good reasons to bet on US resilience, but that will depend on the ability and willingness of American leaders to rebuild the country's strength from within.

Europe has advantages that will reinforce the strength of its markets, and for all Japan's problems, it is still the world's third-largest economy. Most emerging powers will continue to emerge, but some will have more staying power than others.

We now live in a world without global leadership. The need to prevent conflict, grow the global economy, manage growing demand for energy, implement far-sighted trade and investment policies, and counter transnational risks to public health demands leaders who are willing and able to shoulder burdens and enforce compromise.

Leaders have the leverage to coordinate multinational responses. They have the wealth and power to persuade other governments to take actions they wouldn't otherwise take. They pick up the cheques that others can't afford, and provide services no one else will pay for. There are many countries now strong enough to block international action, but none has the power to remake the status quo.

We can't expect global institutions to take up the slack. The G7 group of industrialised democracies has become an anachronism, but the expanded G20 doesn't work either, because there are too many players with too broad a range of interests and values seated around its negotiating table to produce agreement on anything more demanding than high-minded declarations of principle.

Deep-pocketed emerging powers can't decide whether to push for more power within existing institutions like the IMF and World Bank or to try to build new ones.

In short, we are now living with a G-Zero order, one in which no single power or alliance of powers has the muscle, the means and the will to provide the leadership needed to tackle a growing list of transnational threats.

What does this mean for relations among nations and the future of the global economy? In the world's hotspots, regions where the United States has long helped to maintain a delicate balance of power, problems are now more likely than at any time since the end of World War II to become crises. For traditional powers, the issues start at home.

US and European elected officials know that voters tend to support costly, extended military commitments only when they believe that vital national interests are at stake. That's why, from Yugoslavia to Rwanda and Sudan to Syria, they tend to remain on the sidelines for as long as possible.

Given the current demand for austerity on both sides of the Atlantic, we are likely to see both a larger number of local conflicts and an even deeper Western reluctance to engage – particularly in the increasingly complicated and volatile Middle East. In years to come, the Nato intervention in Libya will look more like the exception, and the hands-off approach to Syria's civil war will be the rule.

But conventional conflict is not the only source of trouble. Given the market volatility of the past four years, governments of both established and leading emerging powers are more worried than ever about ensuring they have the means to create jobs and boost growth. That's why the most important instruments of power and influence in coming years will be economic tools like market access, investment rules, and currency policies.

In a variety of ways, governments will slow (in some cases reverse) the free flow of ideas, information, people, money, goods and services that we call globalisation.

Expect great power competition in cyberspace as state-supported industrial espionage becomes a more widely used weapon in competition for natural resources and market share. Some authoritarian emerging players will find new ways to reestablish state control over information and communication, both across and within borders.

Add the shared problem of climate change, the risk of food price shocks, threats to public health and other transnational worries, and the world will lack leadership just at the moment it needs it most.

This state of affairs won't be bad news for everyone, because the G-Zero will produce its share of winners as well as losers.

Over the past 30 years, those states that best adapted to the processes of globalisation thrived, but in an international order in which no single country can afford to lead, those who still operate as if borders are opening, barriers are falling, and the world is becoming a single market will find themselves reacting to events they don't understand.

In years to come, governments that can build profitable commercial and security relationships with multiple partners without becoming overly reliant on any one of them will weather storms more effectively than those that cannot or will not.

For example, Brazil has built solid political ties and lucrative economic relations with the United States, China and a growing number of other emerging market countries. Its economy continues to enjoy access to US consumers, but ties with China, now its largest trade partner, ensure that it isn't overly dependent on US purchasing power for growth.

A serious downturn in the US will still take a heavy toll on Mexico. That's less true for Brazil, which emerged from the 2008 financial crisis and 2009 US recession with much less damage than many other US. trade partners. A set of countries as diverse as Turkey, Vietnam, Canada, and Kazakhstan are actively developing this strategy to suit their own circumstances.

This G-Zero era of transition will pose a unique set of challenges for US policymakers. America will have to learn to do something it doesn't do very well these days: invest in the future. In a country where political leaders focus so much of their energies on winning the next news cycle, and business leaders privilege quarterly profits at the expense of long-term reinvestment, Americans need to look beyond the horizon.

Anyone who believes that American decline is inevitable has chosen to ignore the entire history of the United States and its people. For the time being, Washington can't lead as it did during the second half of the 20th century. The balance of political and economic power has changed profoundly since 1945 – even since 1990.

But the G-Zero cannot last indefinitely, because tomorrow's most important powers, whoever they turn out to be, won't be able to allow it to continue. They will have to put out the fires that have begun to spread across borders.

If Americans can rebuild for the future, the country's underlying strengths – its hard power capacities and its democratic, entrepreneurial values – will ensure that US leadership can again prove indispensable for international security and prosperity.

The capacity to lead in a post-G-Zero world should guide both America's foreign and domestic policies in years to come.