Ten years on, it is clear that the Iraq war fuelled a sea-change in international opinion towards the United States. These movements in foreign sentiment are the most significant since at least the Vietnam conflict, and hold key present-day implications for US policymakers.
Over the course of the past decade, not one but two crosscutting meta-narratives have been at work in international public opinion.
The first is the international growth of anti-Americanism, driven by Iraq and wider perceptions of excessive US power, unilateralism and over-reliance on military might. This was an especially strong impulse from 2003 to 2008 during the Bush administration.
In the run-up to and aftermath of the Iraq war, favourability towards the US, which had spiked upwards after September 11, 2001, went into free fall in many countries. This and the accompanying rise of anti-Americanism is important because it has undercut US soft power and thereby reduced Washington's ability to promote its interests overseas, and indeed those of its allies.
History underlines the role soft power has played in obtaining favourable outcomes for Washington. For example, successive US administrations used soft resources skilfully after the Second World War to encourage other countries into a system of alliances and institutions, such as Nato, the IMF, the World Bank and the UN. The Cold War was subsequently won by a strategy that combined soft and hard power.
The fall-off in international favourability towards the US since Iraq has now been largely arrested, and in most cases, partially reversed. Yet, significant issues persist.
For instance, in eight of 13 key states that were surveyed in both 2002 and 2012 by the annual Pew Global Attitudes Project (Britain, Czech Republic, Germany, Jordan, Mexico, Poland, Russia and Turkey), significantly fewer people now think favourably of the US than they did a decade earlier. This is most clear in the two Muslim-majority countries.
Since 2002, US favourability ratings have halved in Nato ally Turkey from 30 per cent to 15 per cent. The fall in Jordan, another pro-western state, has been from 25 per cent to 12 per cent.
The election in 2008 of Barack Obama, who is more personally popular with foreign publics than Mr Bush, produced an immediate increase in favourability towards the United States. However, since Mr Obama took office, there has been a significant decrease in international approval of US policies, with particular concerns including reliance on drone strikes in the campaign against terrorism.
Support in China for US policies has dropped from 57 per cent in 2009 to 27 per cent, according to Pew. In Britain, France, Germany, Spain and Poland, the average reduction is 15 percentage points.
To be sure, significant ups and downs in international favourability towards the United States are not unprecedented. During the Vietnam War, anti-Americanism increased markedly. There was also significant overseas concern about US policy during the early Reagan presidency following increased tensions with the Soviet Union.
While the US fully recovered from these previous episodes, it remains unclear whether this will happen again. In part, this is because those former rises in anti-Americanism occurred during an era of rigid bipolarity in which US allies regarded the USSR as by far the greater danger and tended to give Washington the benefit of any doubt.
The post-Cold War world is more fluid and uncertain. And, this is where the second crosscutting meta-narrative, which has assumed special prominence since 2008, is key. Relating to the perceived recent decline of the US, it reflects widespread international assessments of the country's record in Iraq and Afghanistan, and the global financial crisis, which is commonly perceived to have accelerated the rise of China and the wider East.
Specifically, there has been sizeable growth in opinion that China will surpass, or has already surpassed, the US as the world's most powerful state. For instance, between 2009 and 2011 alone, there was a at least 10 percentage point increase in public support for this proposition in Spain, France, Pakistan, Jordan, Israel, Poland and Germany, according to Pew.
China's growing prominence has aroused mixed international reactions: in some cases there is considerable anxiety, but elsewhere the perceived shift in the global balance of power is welcomed. Interestingly, numerous Muslim-majority states (where favourability towards the US is generally low) are among those which tend to regard China's rise most positively.
In coming years, the interplay between these crosscutting meta-narratives will be shaped by global events. Even though some international opinion perceives the US to be in decline, there are continuing concerns about how Washington uses its power. The latter could become especially salient again in the event of US military action against Iran.
Conversely, if the US does not soon stage a strong economic recovery, as it did following recessions in the early 1980s and early 1990s when concerns about decline were last voiced, this would fuel international anxiety about a global leadership vacuum, especially if China's rise is perceived to continue unabated.
Whichever way momentum flows, the post-September 11 decade, from Iraq through the global financial crisis, will be remembered as an extraordinary period in terms of international opinion volatility towards the United States. It will take another remarkable event or combination of developments to witness comparable movements of global sentiment in coming years.
Andrew Hammond is an associate partner at ReputationInc. He was formerly a UK Government special adviser and senior consultant at Oxford Analytica