“It’s a tax that comes right off the bottom line,” said EBW’s president, Cory Steeby. “It totally incentivizes you to move out of the United States and build either in Canada or Mexico. These are active conversations right now.”

Mr. Trump portrays his trade war as an unavoidable confrontation aimed at remedying decades of American victimization in the global marketplace. Pointing at trade deficits as indications that Americans have been ripped off — a contention dismissed by many economists — he has unleashed 25 percent tariffs on imports of steel and 10 percent on aluminum.

He has trained special wrath on China, imposing tariffs reaching 25 percent on some $50 billion worth of Chinese imported goods, and 10 percent on an additional $200 billion worth of products. Barring a deal in the next two months or an extension of a fragile cease-fire, Mr. Trump has vowed to increase duties to 25 percent on the whole lot, while threatening to target an additional $267 billion in Chinese imports.

The tariffs have been sold to Americans as a means of forcing multinational companies to make their products in the United States, abandoning China, Mexico and other low-cost centers of industry. But the tariffs are threatening jobs that are already here.

Trade in components has grown in recent years, as American industrial prowess has become increasingly dependent on access to the global supply chain. Back in 2009, American factories imported some 20 percent of the electronic products and computers they folded into their operations, according to an analysis by the United States International Trade Commission. By 2016, the share had risen to 25 percent.