But far too many American companies have shown that their values are for sale. They don’t even haggle much over the price. Last year, the Chinese government demanded that foreign airlines remove references to Taiwan from their websites, because China views Taiwan as a renegade province. The four American airlines affected by the order — American, Delta, Hawaiian and United — present themselves to the world as representatives of the United States. The American flag is painted on the outside of their planes; the interiors are American territory. But instead of standing up for American values, the airlines complied with China’s orders. Other recent examples of capitulation include the fashion retailer Coach destroying T-shirts that read “Hong Kong,” rather than “Hong Kong, China,” and Marriott firing a social media manager in Omaha for “liking” a tweet posted by a group that backs Tibetan independence .

Increasingly, China doesn’t even need to raise an eyebrow for global businesses to blink: American companies are engaged in proactive appeasement. In the new animated movie “Abominable,” released by DreamWorks, a subsidiary of Comcast, one scene includes a map of China with a boundary line encompassing most of the South China Sea. The United States does not recognize that line; neither do the other nations that border the sea, including Vietnam, which pulled the film from theaters. ESPN, a Disney subsidiary, displayed a similar map of China — showing what is known as the “nine-dash line” in the South China Sea — on a recent broadcast.

Comcast and Disney are, of course, free to advocate for the Chinese Communist Party’s position, and against the American and global consensus, in the continuing dispute over China’s international boundaries. But by all appearances, the decisions were both less principled and more pernicious: The companies acquiesced in China’s view of the world simply because that was the path of least resistance.

Some companies have tried to evade the issue by insisting they want to avoid politics altogether. Blizzard Entertainment, a subsidiary of the California video game maker Activision Blizzard, banned a user for shouting “Liberate Hong Kong, revolution of our times” during an online tournament earlier this month, and confiscated $10,000 in winnings. The company, which later returned the money and commuted the ban to a six-month suspension, said it would have taken the same action if a player had shouted in opposition to the Hong Kong protesters. A rival company, the Los Angeles-based Riot Games, announced its own ban on political speech, warning players to “refrain from discussing” political issues, including the Hong Kong protests. (Tencent, a Chinese conglomerate, holds a 5 percent stake in Activision and owns the entirety of Riot.)

Companies face particular pressure on the internet because deference to physical geography is no longer a viable standard. “When in Rome, do as the Romans do,” has lost its meaning. On the internet, one is always at home and always in Rome, too. But there is, or should be, a critical point of difference between American and Chinese internet businesses. Corporations are the creatures of a particular state, however much their executives prefer to think of their operations as multinational. American companies choose to operate under the laws of the United States and to reap the benefits of life in the United States — and they ought to be held accountable for upholding the values of the United States. American companies should feel a responsibility for maintaining the right to free expression in the internet spaces they create and operate. Otherwise, they risk becoming the enforcers of a corporate regime of global censorship that takes its marching orders from Xi Jinping.

Mark Zuckerberg , the chief executive of Facebook, which is banned in China, said this week that the character of the internet must not be taken for granted. “Today, the state of the global internet around the world is primarily defined by American companies and platforms with strong free expression values. There’s just no guarantee that will win out over time.”

Facebook’s role as the private manager of the nation’s public square generates constant controversy, most recently over its refusal to prevent politicians from disseminating clear falsehoods. And the debate over its policies highlights the challenges and contradictions of America’s commitment to free expression. Yet Mr. Zuckerberg is undoubtedly correct that his imperfect company, along with other American tech giants, are the guardians of free expression on the internet. The responsibility of American companies is to maintain that commitment to free expression even if the price is not doing business in China.