Leo Kempel, dean of the Michigan State University College of Engineering, said workers on visas often are needed to build an adequate staff.
"If you're a forward-looking manager, and you're projecting talent needs for the next couple years, you have to meet those talent needs," Kempel said. "If the domestic supply chain isn't supplying what you need, you need to have an additional supply chain. Those H-1Bs can help."
Use of the visas varies among suppliers. Chizuk said Varroc has only "a handful" of employees on such visas. But Downes said the visa program is "very important" for Harman.
"We have a good amount of our work force on some kind of visa," Downes said.
The Trump administration has not publicized a final plan to modify the visa program, but officials have said they want tougher standards to make sure workers coming to the U.S. meet the criteria of having a "specialty occupation."
"I think being more open with inclusive immigration policies would be better," Downes said.
Global suppliers might shift work elsewhere if they can't hire adequate staff in the U.S. Digital projects can be transferred overseas much more easily than physical manufacturing, and most big suppliers have development centers in multiple countries. Varroc, for instance, opened an engineering center in Poland, after assessing educational and skill levels, Chizuk said.
Lack of talent can cause a supplier to assign a project outside the U.S., said OESA's Fream.
"More and more, what we're seeing is they have to take the work overseas where they have the workers," Fream said. "In order to execute [a project] and get it done, they have no choice at this point."
But suppliers prefer to work on projects near customers — in the Midwest for the Detroit 3, she added.
Continental's Reardon agreed, saying proximity to customers is "a huge factor — there's something to having that face time."
Downes said Harman has an operation in suburban Detroit for that reason: "We need to have talent close to customers."
Suppliers' competition in recruiting new-tech expertise isn't limited to auto-industry rivals. The broader battle for technology talent is "fierce," said Michigan State's Kempel.
"The challenge is that the capabilities for the talent that the auto industry needs are also the skill set for consumer electronics, the aerospace industry and other major parts of the economy," Kempel said.
Suppliers say they have effective ways to market themselves to prospective hires — emphasizing the opportunities in a global company, the stability they provide and projects that improve people's lives.
But even so, they say the limited supply of graduates in science, technology, engineering and math — known as STEM fields — in the U.S. makes it hard to fill all jobs with U.S. citizens. A survey by the World Economic Forum in 2016 showed that China had 4.7 million recent STEM graduates, India had 2.6 million, and the U.S. had 568,000.
"From a U.S. perspective," Reardon said, "we don't have the number of students in STEM disciplines."