For all their bitter differences, President Obama and Governor Romney share one overwhelming challenge. Whoever is elected will face the growing reality that the greatest risk to global stability over the next 20 years may be the nature of America itself.

Nothing – not Iranian or North Korean nuclear weapons, not violent extremists or Mideast instability, not climate change or economic imbalances – will shape the world as profoundly as the ability of the United States to remain an effective and confident world player advocating its traditional global purpose of individual rights and open societies.

That was the conclusion of the Global Agenda Council on the United States, a group of experts that was brought together by the World Economic Forum and that I have chaired. Even more intriguing, our group tested our views on, among others, a set of Chinese officials and experts, who worried that we would face a world overwhelmed by chaos if the U.S. – facing resource restraints, leadership fatigue and domestic political dysfunction – disengaged from its global responsibilities.

U.S. leadership, with all its shortcomings and missteps, has been the glue and underwriter of global stability since World War Two – more than any other nation. Even with the world experiencing its greatest shift of economic and political power since the 19th century, no other country is emerging – or looks likely to emerge – that would be as prepared or equipped to exercise leadership on behalf of the global good.

Yet many in the world are questioning the role of U.S. leadership, the governance architecture it helped create and even the values for which the U.S. stands. Weary from a decade of war and strained financially, Americans themselves are rethinking whether they can afford global purpose.