S&P 500 companies with the highest sales exposure to the U.K. include eBay , PayPal and News Corp. , according to Goldman. It said those companies had a greater than 11 percent exposure. Among the top 20 companies Goldman cited, Newmont Mining had the biggest exposure — 75 percent.

"The impact of Brexit on aggregate US equity earnings will likely be limited, irrespective of the outcome," Goldman Sachs analysts said in a note to investors. "However, Brexit uncertainty remains a concern for stocks with the highest U.K. exposure."

U.S. companies in the S&P 500 that have significant revenue from the U.K. are raising concerns among investors because of the Brexit uncertainty.

Global markets largely shrugged off Prime Minister Theresa May's historic loss last week, with Parliament voting 432 to 202 in opposition of her Brexit plan. U.S. stock indexes opened slightly higher the day after that vote but were moving with greater tenacity in response to U.S.-China trade talks.

With only two months until the U.K.'s scheduled departure from the European Union, Brexit uncertainty is looming over some U.S. companies.

The Goldman analysis shows that throughout recent months of political uncertainty, specifically from January through mid-December 2018, the British pound fell 7 percent to the U.S. dollar. In the same period, S&P 500 stocks with high U.K.-exposure lagged U.S.-focused stocks by more than 1,000 basis points, according to the research. Conversely, this group of stocks outperformed domestic-facing stocks by 190 basis points since Dec. 10, when May decided to delay a Brexit vote, a move that also boosted the pound by 3 percent.

The analysts said investors should expect the pound to rise along with this subset of U.K.-exposed stocks should a Brexit deal pass in the near future. However, even with the prospect of short-term gains, experts raised growth concerns for the most exposed S&P 500 companies once Brexit is solidified.

"Ten percent or higher is notable," said Peter Boockvar, the chief investment officer of Bleakley Advisory Group, referring to U.K.-exposed companies. "Any clip to revenue growth in one particular region could have a more pronounced effect because of an offset somewhere else," Boockvar continued, citing the global economic slowdown.

Global uncertainty has been a drag on global markets in recent months, and last week's momentous string of events in Parliament has done little to quell investor turmoil over the U.K.'s departure.

Following the collapse of her two-year divorce plan from the EU scheduled for March 29, May narrowly survived a vote of no confidence in Parliament. She then presented lawmakers with an alternative plan on Monday, which received criticism for its staunch resemblance to her original strategy.

Parliament will debate on the new proposal with an expected vote on Jan. 30. And despite a push back from opposition leaders, May also told lawmakers she could not rule out the possibility of a no-deal Brexit and did not believe there was enough support for a second referendum on whether to leave the European Union.

"At this point, all businesses want to know what happens next, regardless what the details are," Boockvar said. "It's just, 'Let's get on with this. Enough is enough.'"

Since the U.K.'s vote to leave the bloc more than two years ago, concerns have largely surrounded the macro economic implications of Brexit. Only 1 percent of all S&P 500 sales come from Britain. Yet for companies and investors with high exposure to the U.K., experts predict a continued period of volatility at the very least.