Commanding respect: but Iraq does not consume President Obama's attention as it did his predecessor's. Photograph: White House Photo / Pete Souza

This year’s anniversary of the terrorist attacks of September 11 2001 offers an interesting moment to assess the way President Obama has sought to redefine America’s role in the world and to gauge both the potential and the risks inherent in his approach.

Seared by the memory of the attacks, the global war on terror became the near total fixation of the Bush presidency. The wars in Afghanistan and then Iraq consumed the attention of senior US policymakers. Just as significantly, the administration ended up conflating the apolitical, religious fanaticism of al-Qaeda and its regional offshoots with a range of insurgencies and nationalist movements which used terrorist tactics to try to achieve their local political goals.

For much of the eight years from 2001 to 2008, the results of this fixation were negative: dogged US support for an increasingly unreliable President Musharraf in Pakistan; closing off avenues to negotiate with Iran on its nuclear programme because of its support for Hizbollah and Hamas; and a dead-end to the peace process between Israelis and Palestinians. In addition, setting aside some important strategic initiatives towards India and the continued enlargement of NATO, much of the rest of the world, from Latin America to south-east Asia, was left on the diplomatic backburner.

In contrast, the Obama administration appears determined to consider the fight against international terrorism and violent extremists as only one among the many important facets of a far more expansive and traditional portfolio of US international priorities.

Despite the deep economic crisis at home, President Obama and senior members of his team have launched in just their first six months a stream of important diplomatic initiatives towards Russia, India, Iran, Latin America, Israelis and Arabs, and Turkey. This is in addition to addressing the critical global challenges of combating climate change, rewriting international financial regulations and controlling nuclear weapons proliferation.

In one sense, this diplomatic onslaught is not so remarkable. The United States, which is still the world’s most powerful nation with the most extensive range of alliances and institutional roles, is simply re-engaging in the totality of its areas of interest and potential leadership.

Yet America will find it far harder than before to assert its influence in many of these areas. The country’s international economic leadership has been undercut by the global impact of its recent domestic economic failures. Rising and old powers, such as China, India, Brazil and Russia, may not match the US in their global reach, but each now play dominant regional roles that limit America’s sway. The failure of its recent efforts at democracy promotion has entrenched a deep scepticism around the world over how Washington’s international aspirations and values are translated into actions. All in all, the Obama administration faces strong “antibodies” around the world to the reassertion of US leadership.

Not surprisingly, therefore, especially this early into the presidency, the world is still watching and waiting to see whether Washington’s new approach to external relations can deliver results.

This is where this anniversary of the attacks of September 11 becomes all the more important. One major new terrorist attack on US soil – or, perhaps even more damagingly, a series of smaller attacks – could lead to a visceral reaction that would send all of these new initiatives into reverse.

As impressed as much of the world is with Obama’s new foreign policy, many Americans are not impressed by the emerging world order – one in which US leadership is increasingly challenged, its allies are ambivalent in their support, and Washington’s long-standing vision of a world of increasingly open markets and democratic governments can no longer be taken for granted. The domestic pressures on the Obama administration for dramatic action beyond its shores in response to a new terrorist attack would be immense.

It is vital, therefore, that President Obama be able to take his administration’s diplomatic initiatives to their next level as soon as possible. Statements of intent must give way to negotiations and agreements. It is equally vital that America’s allies in Europe, Asia, the Middle East and other parts of the world offer real and practical support to these initiatives. In so doing, they will help anchor the United States into its process of international re-engagement. They will also strengthen its political resilience to cope with whatever unpredictable future shocks take place in what remains a dangerous and unpredictable world.