Chinese foreign direct investment in the United States fell to $5.4 billion in 2018 from a peak of $46.5 billion in 2016, a drop of 88 percent, according to data from Rhodium Group, an economic research firm. Preliminary figures through April of this year, which account for investments by mainland Chinese companies, suggested only a modest uptick from last year, with transactions valued at $2.8 billion.

“I certainly hear in conversations with investors a lot of concern about whether the U.S. market is still open,” said Rod Hunter, a lawyer at Baker McKenzie who specializes in foreign investment reviews. “You have a potentially chilling effect for Chinese investors.”

A confluence of forces appear to be at play. A slowing economy and stricter capital controls in China have made it more difficult for Chinese investors to buy American, according to trade and mergers and acquisitions advisers. Mr. Trump’s penchant for imposing punishing tariffs on Chinese goods and an increasingly powerful regulatory group that is heavily scrutinizing foreign investment, particularly involving Chinese investors, have also scared businesses in both countries.