American companies sold more than $200 billion in computers and electronic goods to foreign buyers last year, including $18 billion to China. And while that was a small part of the United States’ $2.5 trillion in total exports last year, the broader tech sector has accounted for an outsize share of economic growth in recent years.

Anything that disrupts the global supply chains the industry relies on could threaten American economic growth, said Torsten Slok, chief economist for Deutsche Bank. Semiconductor sales, he said, have proved to be a reliable indicator of the direction of the broader economy — and sales have been falling this year.

“We will find out soon if the economy was strong enough to withstand this,” Mr. Slok said.

If the electronics industry sneezes, few places will catch a cold as quickly as Portland. The industry employs close to 40,000 people in Oregon, including 20,000 at Intel, the state’s largest private employer. Oregon exported $2.7 billion in electronics goods to China last year, more than any state other than California — a total that doesn’t include companies, like ControlTek, that are just across the Columbia River in Washington State.

Founded in 1971, ControlTek has weathered the rise of Japan and then China. Today, the company and its 140 employees don’t try to compete directly with the high-volume factories in China.

Instead, ControlTek, like American manufacturers in other industries, has survived by carving out a niche based on quality and service. Its plant in Vancouver, Wash., has state-of-the-art machines that place components — integrated circuits, capacitors, resistors and other devices, some barely big enough to see with the naked eye — onto circuit boards destined for medical devices, aircraft and even pitching machines. But it also has employees hand-soldering parts beneath high-powered magnifying glasses, the kind of personalized attention that can look like an anachronism on today’s highly automated factory floors.

When the first round of tariffs went into effect last year, ControlTek executives had no idea how they would be affected, or even how to find out. The software for tracking inventory showed the company’s suppliers, but not where those suppliers got their material.