The New York Times showed that Trump tariffs on cars will boomerang and hurt Trump voters in South Carolina, Tennessee, and Alabama.

“BRUSSELS — President Trump has complained about seeing too many German cars on Fifth Avenue, and threatened heavy tariffs on the companies that produce them. There is a good chance, though, that those Mercedes-Benzes and BMWs were not only made in the United States, but made by workers who voted for Mr. Trump.

“European companies have turned Alabama, South Carolina and Tennessee into auto manufacturing powerhouses in recent years, churning out cars not just for American buyers but also for export to China and Europe. Germany’s three biggest carmakers all have facilities there, and Volvo Cars, which is owned by a Chinese company but based in Sweden, began producing at a new plant in South Carolina just last month.

“Yet being major employers in regions that voted heavily for Mr. Trump has not protected them.

“With barely a peep of resistance from his own party, the president has threatened tariffs — expected to be 20 percent — on imported cars and car parts. In a prelude to such a move, he has ordered an investigation into whether the imports pose a threat to national security. Trade restrictions could be put in place within months. And if he follows through, the European Union has pledged to retaliate.

“The damage would be far-reaching, draining an estimated $14 billion from the United States economy. If other countries retaliated, the cost would skyrocket to nearly $300 billion, the European Union’s Washington delegation said last week.

“Carmakers, both foreign and domestic, say such penalties would severely damage their lines of supply, interfere with exports and eventually force them to curtail operations in, of all places, Republican strongholds.

“Mr. Trump won 63 percent of the vote in Spartanburg, S.C., home of BMW’s biggest factory anywhere in the world. But Allen Smith, president of the Spartanburg Area Chamber of Commerce, said the president’s tariffs would threaten the region’s livelihood.

“For BMW and its many, many suppliers scattered across the state and region, you’re talking tens of thousands of jobs,” Mr. Smith said. “We would all agree with the president’s overall aim to improve trade with America’s interests top of mind. But getting to that end by inflicting so much pain on American business is the wrong approach.”

“Mr. Trump’s threat to impose auto tariffs would be the latest manifestation of his willingness to alienate longtime allies and American companies, ostensibly to protect domestic jobs. He has already imposed levies on steel and aluminum from the European Union, Canada, Mexico and other nations, and on Friday will place tariffs on $34 billion worth of Chinese products.

“But this new front in the trade war carries substantial risk not just for the auto industry but for Mr. Trump and Republican officeholders nationwide, given the impact that a full-blown trade war could have on American jobs tied to the auto industry.

“Virtually all cars made in the United States contain imported parts. Unlike steel and aluminum tariffs, whose costs may not be obvious to most consumers, automotive levies would show up in showrooms within weeks. Sticker prices would rise by hundreds if not thousands of dollars. That is why Ford and General Motors, alongside foreign automakers, have also roundly condemned the protectionist measures.

“The times are gone that a producer was only headquartered in one country with production in that country and exporting from that country to the rest of the world,” said Erik Jonnaert, the secretary general of the European Automobile Manufacturers’ Association, in an interview in Brussels.

“The economic impact would be greatest in a triangle demarcated by BMW’s factory in Spartanburg; Daimler’s Mercedes complex in Tuscaloosa, Ala.; and Volkswagen’s plant in Chattanooga, Tenn…

“Over time, the European carmakers have expanded their operations in those regions not only to build vehicles for American buyers, but also to serve customers in places like China. Last year, Daimler added 900 jobs to its American operations, which also include truck factories, and it is investing $1 billion to expand the Tuscaloosa operation to produce electric vehicles and batteries.

“Mr. Trump’s contention that these companies may present a threat to American national security, though, has thrown that growth into doubt.

“BMW exports 70 percent of the vehicles that it makes in Spartanburg, about 270,000, helping to reduce the trade deficit that Mr. Trump often complains about. BMW plans to add 1,000 jobs in Spartanburg as part of a $600 million expansion. If trade tensions continue to escalate, BMW warned in a letter on June 28 to Wilbur Ross, the commerce secretary, the result could be “strongly reduced export volumes and negative effects on investment and employment in the United States.”