Several years before Donald J. Trump entered politics, Apple and its partners built massive factories across China to assemble iPhones. Mr. Trump first campaigned for president by promising his supporters that he would force Apple to make those products in America.

Nearly a decade later, little has changed. Instead of bringing its manufacturing home, Apple shifted some production from China to India, Vietnam and Thailand. Almost nothing is made in America, and an estimated 80 percent of iPhones are still made in China.

Despite years of pressure, Apple’s business is still so dependent on China that the tech giant can’t operate without it. Moves by the Trump administration to change Apple’s behavior risk damaging the world’s most valuable publicly traded company. And any serious effort to move Apple’s production to the United States — if that is even possible — would take a titanic effort by both the company and the federal government.

In the four days after President Trump announced taxes on Chinese exports of 145 percent last month, Apple lost $770 billion in market capitalization. It regained some of those losses after Mr. Trump gave consumer electronics manufacturers in China a temporary reprieve.

On Thursday, Wall Street analysts expect Apple to report that sales increased 4 percent in the most recent quarter, partly because people rushed to buy iPhones before the tariffs kicked in. The report offers Wall Street analysts an opportunity to grill Apple’s chief executive, Tim Cook, about the risk of future tariffs, price increases and the company’s future in China and the United States.

An Apple spokesman declined to make any company executives available for this article. The company said this year that it would invest $500 billion in the United States over the next four years and begin making artificial intelligence servers in Houston in 2026.