The chamber declined to say if it supported any measures to curb smoking.

The chamber, a private nonprofit that has more than three million members and annual revenue of $165 million, spends more on lobbying than any other interest group in America. For decades, it has taken positions aimed at bolstering its members’ fortunes.

While the chamber has local outposts across the United States, it also has more than 100 affiliates around the world. Foreign branches pay dues and typically hew to the U.S. Chamber’s strategy, often advancing it on the ground. Members include both American and foreign businesses, a symbiotic relationship that magnifies the chamber’s clout.

For foreign companies, membership comes with “access to the U.S. Embassy” according to the Cambodian branch, and entree to “the U.S. government,” according to the Azerbaijan branch. Members in Hanoi get an invitation to an annual trip to “lobby Congress and the administration” in Washington.

Since Mr. Donohue took over in 1997, he has steered the chamber into positions that have alienated some members. In 2009, the chamber threatened to sue if the Environmental Protection Agency regulated greenhouse gas emissions, disputing its authority to act on climate change. That led Nike to step down from the chamber’s board, and to Apple’s departure from the group. In 2013, the American arm of the Swedish construction giant Skanska resigned, protesting the chamber’s support for what Skanska called a “chemical industry-led initiative” to lobby against green building codes.

The chamber’s tobacco lobbying has led to confusion for many countries, Dr. da Costa e Silva said, adding “there is a misconception that the American chamber of commerce represents the government of the U.S.” In some places like Estonia, the lines are blurred. The United States ambassador there, Jeffrey Levine, serves as honorary president of the chamber’s local affiliate; the affiliate quoted Philip Morris in a publication outlining its priorities.

The tobacco industry has increasingly turned to international courts to challenge antismoking laws that countries have enacted after the passage of the W.H.O. treaty. Early this year, Michael R. Bloomberg and Bill Gates set up an international fund to fight such suits. Matthew L. Myers, president of the Campaign for Tobacco-Free Kids, an advocacy group that administers the fund, called the chamber “the tobacco industry’s most formidable front group,” adding, “it pops up everywhere.”