Ten years on, it is clear that the Iraq invasion fuelled a sea-change in international opinion toward the United States. These movements in foreign sentiment are the most significant since at least the Vietnam War, and hold key present day implications for US policymakers.
Over the course of the past decade, not one but two cross-cutting 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 United States, which had spiked upwards after 9/11, went into freefall in many countries. This and the accompanying rise of anti-Americanism is important, primarily, 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 World War II 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 falloff in international favourability towards the United States since Iraq has now been largely arrested, and in most cases, partially reversed. Yet, significant issues persist.
For instance, in 8 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 United States than they did a decade earlier. This is most clear in (but by no means restricted to) Muslim-majority countries.
Since 2002, for instance, US favourability ratings have halved in NATO ally Turkey from 30% to 15%. The fall-off in Jordan, another pro-Western state, is even bigger in percentage terms from 25% to 12%.
The election in 2008 of President Obama, who is more personally popular with foreign publics than Bush, prompted an immediate increase is favourability toward the United States. However, since Obama took office, there has been a marked fall in international approval of US policies, with particular concerns including the reliance on drone strikes in the campaign against terrorism.
Support in China for US policies has dropped from 57% in 2009 to 27%, according to Pew. In Britain, France, Germany, Spain and Poland, the average reduction in support is 15 percentage points.
To be sure, sizable falloffs 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 United States 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 Soviet Union 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 cross-cutting meta-narrative, which has assumed special prominence since 2008, is key. Relating to the perceived recent decline of the United States, this impulse 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 international opinion that China will or already has surpassed the United States as the world's most powerful state. For instance, between 2009 and 2011 alone, there was an at least 10 or more percentage point increase in public support for this proposition in countries as diverse as 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 shift in the global balance of power is welcomed. Interestingly, many Muslim-majority states (where favourability towards the United States is generally so low) are amongst those who tend to regard positively China's perceived rise.
In coming years, the interplay between these cross-cutting meta-narratives will be shaped by global events. Even though some international opinion perceives the United States 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 United States 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-9/11 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 in coming years to witness comparable movements of global sentiment.
Andrew Hammond is a former UK Government Special Adviser and Senior Consultant at Oxford Analytica