Roberts said American investors are showing concerns the problems European banks face may not be contained to that continent. Investors are watching how Europe is managing its debt crisis, which has already led to bailouts for Greece, Ireland and Portugal.
Meanwhile, investment bank Morgan Stanley cut its global growth forecast for the year to 3.9 percent, down from a previous forecast of 4.2 percent. The bank cited an "insufficient" policy response to Europe's sovereign debt woes and the possibility of fiscal tightening that could make it harder for businesses to borrow.
Morgan Stanley, which also cut its China growth forecast for next year, wrote that the U.S. and Europe are "dangerously close to recession."
"Recent policy errors, especially Europe's slow and insufficient response to the sovereign crisis and the drama around lifting the U.S. debt ceiling, have weighed down on financial markets and eroded business and consumer confidence," London-based analyst Joachim Fels wrote in the report.
Roberts said Morgan Stanley's report confirmed what many investors already expected.
"Everyone is starting to think the economy is starting to fall apart and asking, 'who is going to bail us out?'" Roberts said. He said investors looking for safe havens in Treasury bonds and gold have led to a decrease in Treasury yields and a spike in gold.
The Associated Press contributed to this report.