Commodities-sensitive U.S. firms such as Caterpillar invested heavily in China in an attempt to ride the economic boom there. Consumer-oriented companies like Apple followed, trying to target Chinese consumers.
Copper prices, often seen as an indicator of China's industrial health, are down more than 40 percent from a 2011 peak, and Caterpillar is on track for its first four-year decline in sales and revenues. And since the fiscal second quarter of this year, Apple has reported year-over-year declines of more than 25 percent in Greater China sales, versus double-digit growth previously.
"If you're waiting for the booming Chinese consumer ... it's just not on the way. The upside is just not what some consumer firms were hoping for," said Derek Scissors, chief economist at China Beige Book International, which regularly surveys Chinese businesses.
China is also maturing as an economy. The country boasts many iPhone rivals, the world's biggest drone maker and strong, homegrown e-commerce market.
"Chinese business people and Chinese businesses have a lot of money, and they can afford to buy" major U.S. companies' Chinese units, said Geoffrey Sant, partner in the trial department of Dorsey & Whitney and a former professor of U.S. law in Beijing. China has long required most U.S. firms to partner with Chinese counterparts in order to do business there in the first place.
"I wouldn't necessarily categorize these sales as 'I'm wanting to get out of China,' but more as 'I'm willing to buy' [for] a lot of cash," he said.
Now U.S. firms may need to try a different China strategy in order to thrive there.
"I do think there are new firms that are finding China as interesting as everyone used to," Scissors said. He pointed to opportunities in senior care, environmental protection and asset management, especially as China copes with massive levels of domestic debt.
Another possible opportunity may lie in financial services. In the last few months, fund management firm Vanguard and JPMorgan Asset Management both received approval to establish wholly owned subsidiaries in Shanghai.
"We see this as the first step of our mission to lower the cost of investing in China and help millions of local investors reach their goals," Vanguard spokeswoman Linda Wolohan said in an emailed statement.
— CNBC's Jane Wells contributed to this report.