The nation's favourability ratings are in free fall. A survey published last week by the Pew Research Centre in Washington, DC, showed they tumbled from 75 per cent to 48 per cent in Britain over the past year. And that was just the good news. In France they were down from 63 per cent to 31 per cent, in Russia from 61 per cent to 28 per cent and in Turkey from 30 per cent to just 12 per cent.

Who cares? Plummeting favourability ratings have not deflected President George W. Bush from pursuing the war in Iraq. But beyond the political realm, big American consumer brands such as Coca-Cola, McDonald's and Marlboro are paying a price as boycotts spread from the Middle East to the rest of the world, especially Europe. One German website, www.consumers-against-war.de, is urging people to boycott 27 US companies, from American Express to Walt Disney.

It is important to keep these developments in perspective. So far, the boycotts have been mainly symbolic and the effects small in the context of US brand-owners' global operations.

Conceivably, too, the current phase of anti-Americanism could prove short-lived. "I don't think America will remain that unpopular for that long. It's just going through an extremely clumsy phase in the way it presents itself," says Wally Olins, a London brand consultant who has worked on many country rebranding projects. "I don't believe America is likely to sustain over a long period of time policies that are objectionable to a sufficient number of people for them to turn away from American products."

Yet the decline in America's image is more than just a war-related hiccup. Last year, Pew carried out a much bigger survey of worldwide attitudes towards the US, interviewing 38,000 people in 44 countries. It found that in 19 of the 27 countries for which comparisons could be made, people viewed America less favourably than they had two years earlier, in spite of the outpouring of public sympathy for the US after the terrorist attacks of September 11 2001.

Reassuringly for US brand-owners, people seemed more troubled by American policies than by American products. Many complained that the US was too unilateralist in its approach to global problems and accused it of pursuing policies that increased the rich/ poor divide. They also resented the intrusion into their countries of American customs and ideas. Yet American technology was widely admired and young people especially were happy to embrace America's popular culture, as represented by its television programmes, music and films.

Carroll Doherty, Pew's editor, says people may complain about the spread of American culture but they seem to like its artefacts. "If it's a product they like and enjoy," he says, "they're going to buy it whether or not they approve of the country it comes from."

John Quelch, professor of business administration at Harvard Business School, agrees. "At the margin, there are sure to be some negative consequences that flow out of this. But most teenagers, who represent the highest consumption for brands like Nike shoes and Coca-Cola, are not desperately fascinated by making the equation from what's happening in the geopolitical scene to their own fashion behaviour."

Others are not so sure. Shih-Fen Chen, a professor of international marketing at Brandeis University's Graduate School of International Economics and Finance in Massachusetts, says people underestimate the extent to which a positive national image can help companies sell their products overseas. "In most of the world," he says, "American products enjoy a competitive advantage because the national image is one of a freedom-loving society with respect for human rights. The war will create a hostile dimension that could cost American companies billions of dollars."