Amid the tumult, other markets considered alternative safe havens to the United States have gained. Yields on German government bonds, which serve as the benchmark for the eurozone, fell on Wednesday, indicating strong demand. Gold prices rose, too.

“The global safe-haven status is in question,” said Priya Misra, a portfolio manager at J.P. Morgan Asset Management. “Disorderly moves have happened this week because there is no safe place to hide.”

“Optically, in some countries now you don’t want to show an overweight position, or maybe even an equal-weight position, in the U.S.,” said Peter Tchir, head of macro strategy at Academy Securities, an investment firm.

In a social media post on Wednesday, the former U.S. Treasury secretary Lawrence H. Summers said the broader sell-off suggested a “generalized aversion to US assets in global financial markets” and warned about the possibility of a “serious financial crisis wholly induced by U.S. government tariff policy.”

“We are being treated by global financial markets like a problematic emerging market,” he wrote.

“If they can do these extreme restrictions on trade, even with the closest allies, can they do restrictions on capital flows as well?” Mr. Nordvig asked. “Nobody knows. There is no limit here.”