Shares of the Nos. 2 and 3 largest publicly traded U.S. car dealership chains with substantial U.K. interests got clobbered on Friday and sank again early Monday as investors struggled to assess the fallout from last week's vote by Great Britain to leave the European Union.

After losing more than 10% of its value on Friday, Penske Automotive Group (PAG) - Get Report  fell Monday by 4.1%. Group 1 Automotive (GPI) - Get Report , which closed down more than 6% on Friday, fell 4.5% in trading early Monday. 

Investor nervousness regarding these two stocks likely centered on how the U.K.'s eventual exit from the EU could affect the automotive business in that country and the repercussions for retailers of new and used vehicles to British citizens and corporations.

Earl Hesterberg, chief executive of Group 1, said in an emailed statement that "money moves so fast these days, market reactions are very pronounced in the short term." Yet they adjust to reality "better than most people think."

In the first quarter, Group 1's 29 stores in the U.K. accounted for 18% of unit sales and $431.9 million of the company's $2.61 billion of revenue.

He added: "Uncertainty is the biggest issue for our business and auto sales in the short term. Of course currency translation will be a headwind for the near term as well. Our management has been around a bit so they don't fluster easily."

Penske Automotive, whose CEO is Roger Penske, derives about one-third of its revenue and its profit from its 94 U.K. stores.

Tony Pordon, executive vice president, said in an emailed statement that firm conclusions about the repercussions of "Brexit" are difficult since the event is "unprecedented." The most likely impact will come as a result of the currency risk inherent in a weaker pound, which must be translated for Penske Automotive's financial results.

"Brexit will take several years to work its way through so this will be a long process," he said. He noted that the U.K. economy has been strong, unemployment and interest rates low. Additionally, the company sells used and new cars. "People have to drive something," he said.

The biggest U.S. automotive retailer, AutoNation  (AN) - Get Report , has sidestepped overseas expansion. AutoNation's shares were off about 2.2% in trading Monday.

Prior to the Brexit vote, shares of all three auto retailers were off about 30% from a year ago, largely on the expectation that the nearly seven-year expansion of new-vehicle sales in the U.S. was nearing an end. Despite forecasts of a slowdown, automotive sales have remained strong. Thus, it looks as though much of the negative expectation for big auto retailers is being reflected by their current prices -- which may mean a long-term opportunity for value-oriented investors.

Doron Levin is the host of "In the Driver Seat," broadcast on SiriusXM Insight 121, Saturday at noon, encore Sunday at 9 a.m.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.