Numerous non-US airlines including Air Canada, Lufthansa, British Airways and Qantas have already made changes to their websites after China's Civil Aviation Administration sent a letter to 36 foreign air carriers this year.
Representatives for Delta and United made similar statements.
"Like other carriers, American is implementing changes to address China's request", said Shannon Gilson, a spokeswoman for American, the world's biggest airline.
The company doesn't fly to Taiwan but does sell tickets through a marketing relationship with China Airlines Ltd., which flies nonstop from Taipei to Honolulu.
Other global airlines, including Lufthansa, Air Canada and Singapore Airlines, had already changed their website classifications of Taiwan to "Taiwan, China" ahead of the deadline in order to avoid penalties. The airlines, however, didn't go so far as to say that Taipei is part of China.
China, however, is a rapidly growing airline market with a booming middle class that is eager to travel.
Beijing set 25 July as a deadline for companies and airlines to remove references to Taiwan as anything but a Chinese territory on their websites. The mainland has increasingly used its economic and political clout to pressure countries and corporations to stop recognizing the island's government.
But not all airlines have applied the change in the same way: Korean Air and Asiana Airlines, for example, have opted to list destinations by city and airport.
China has claimed Taiwan as a breakaway province since the sides split during a civil war in 1949 and threatens to use force to annex it.
China represents a key air travel market for many worldwide airlines and could become the world's largest by 2022, overtaking the United States, the global Air Transport Association industry group has projected.
Beijing hailed "positive steps" as major U.S. airlines and Hong Kong's flag carrier moved to comply Wednesday with its demand to list Taiwan as part of China, sparking anger on the island.
Searches on the websites of Delta and United still mentioned Taipei as being in Taiwan.
American, which in searches previously displayed the main airport in Taiwan's capital city as "TPE, Taiwan", switched to "TPE-Taoyuan International" and it dropped "Taiwan" from search results. Democratically governed Taiwan has been a central issue among, especially after the Trump administration expanded ties with the island's pro-independence president, Tsai Ing-Wen.
"We have told China that the United States strongly objects to China's attempts to compel private firms to use specific words of a political nature in their publicly available content", a spokesperson for the U.S. Embassy in Beijing said Tuesday. "At the same time, we hope they can abide by China's rules and regulations".
"I was not aware that the companies said that they would fold to the Chinese government", she added, referring to the airlines.