Offer to buy the world a Coke and you'll probably find plenty of takers. But try to sell the iconic American drink, and you might meet with some ambivalence among youths these days, particularly abroad. That's according to a recent study that compared big global brands it considered "teen relevant," gathering feedback from thousands of youths in 13 countries - including the United States.

Coca-Cola still topped the chart in terms of name recognition, followed by McDonald's. But Coke fell to eighth place when it came to likeability, and the burger chain dropped all the way to No. 32. Disney and America Online also nose-dived in appeal.

The top three affinity slots went to Sony (Japan), Nokia (Finland), and Adidas (Germany). Top US finisher: Nike at No. 4, a somewhat surprising result given that US firms have traditionally wielded a collective hegemony with this very desirable demographic.

"If you wanted to characterize what the 'cool' brands were for global teens 10 years ago, what they had in common was that a lot of them were from America," says Chip Walker, executive vice president of Energy BBDO, the market-research firm that ran the study, called GenWorld.

Branding experts differ on the chief causes of the apparent loyalty shift. They cite factors that range from deft, low-key marketing and product innovation by firms to a political pushback by young consumers. But the study suggests that control is slipping from brands that try to impose images on teens rather than reflecting teens' perceptions of themselves.

And experts agree that marketers and even government policymakers would be unwise to shrug off any shifts. The buying habits of today's teen market - reportedly worth some $170 billion a year in the US alone - stand to alter the economic landscape.

Researchers hesitate to assign a dollar figure to the spending of the so-called "global teen" market, with its shared cultural reference points. In 1998, a United Nations report estimated there were 270 million such teens worldwide in the 15-18 age bracket.

Smart brands win teen market share by allowing teens to be part of a brand "story," experts say. Mr. Walker names the global teen "passion points" as music, media, sports, and communication.

"Adidas, and really all the brands at the top of the list, have 'imaged' themselves in the same way that these kids see themselves," says Schuyler Brown, a trend-spotter and former managing director of Euro RSCG, an international marketing-service agency.

"They're global brands that have really deep tentacles and draw on the local culture very well," she says, tying promotions to local soccer teams, for example. Becoming ubiquitous in a culture can attract entire teen enclaves. Suddenly, "everybody has a Nokia phone," she says.

It helps to have an ear for "global teen" values, some of which extend across cultures, according to the GenWorld study.

"[The Adidas slogan] 'Impossible is Nothing' resonates with this generation almost like no other campaign that I've seen," says Walker, who calls global teens engaged, optimistic, and connected.

Product details matter. Nokia has held sway over American rival Motorola, he says, because of their emphasis on cellphone design. Motorola, however, has focused on internal engineering.

Politics, too, can play a role. Many teens abroad are developing a "new nationalism," says Ms. Brown. American brands used to carry edgy cultural cachet, she says. Today, "teens around the world have become disenchanted with the mythological portrayal of American youth." Sometimes that nationalism finds an outlet in satire and humor at America's expense. "It's been very easy to spoof America in the past few years," Brown says.

Others say that disenchantment could have a dire economic effect. "America has taken some very unpopular positions on the [Iraq] war and the environment," says Irma Zandl, principal of Zandl Group, a marketing consultancy. "American brands are starting to suffer as people vote at the cash register," she writes in an e-mail.

Ms. Zandl points out that a number of leading-edge brands, such as Apple, even take care to point out that their products (such as iPod) are designed, if not made, in California, versus the US at large - a move she reads as a kind of separation.

Still, not all experts see country of origin as an issue with teens. Some doubt whether many US teens could name Adidas's home base. Marian Salzman, author of the 2003 book "Buzz," points out that teens outside the US have "effectively localized" the US brands they like.

"I don't think there are any concerns on the part of teens as to where stuff comes from," says Jim Taylor, vice chairman of the Harrison Group, a marketing agency. He has worked with the trend-watcher firm Intellisponse on its annual surveys of what (primarily US) teens want.

"Kids don't necessarily [even] sort out the difference between store brands and product brands," says Mr. Taylor, pointing to the rise of Hollister, a store brand in apparel that has surged of late.

For today's teens, he says, online buzz is king, and peers hold the most sway. "What applies to young people is 'Did it break? And did my friends say it was cool?' [It's an] opinion process that goes on through IMs and text-messaging, and it applies to everything from movies to cargo pants."