Here's why Apple couldn't build the 2013 Mac Pro in the U.S.

In 2012, Apple CEO Tim Cook publicly announced that one line of Apple's Mac products will be made in the United States.

Well, it never happened for precisely the reasons you'd think of: Supply chain issues. More precisely, according to a New York Times report Monday, Apple couldn't find enough screws to build the Mac Pro in the United States.

The report shares details about Apple's struggles to build the Mac Pro in Austin, Texas, citing people who worked on the project. There, Apple relied on a 20-employee machine shop that couldn't produce more than 1,000 screws per day. The shortage of screws, combined with other issues, delayed the project, and ultimately, Apple had to order screws from China.

In another example, Apple had ordered 28,000 screws from a U.S. company, based in Lockhart, with the company's president often delivering the screws to Apple himself, in his Lexus sedan.

While interesting, the report merely reinforces the notion that it's extremely tough for a company like Apple, which often needs enormous amounts of custom parts made in a short time frame, to move its manufacturing away from China.

This is due to a multitude of reasons; Chinese workers can typically be hired for lower wages, they're ready to work around the clock, and there's just more factories ready to build the type of parts Apple wants at the volumes that Apple needs.

Apple is trying, though; the NYT report notes that the company is trying to diversify its supply chain, but mostly in India and Vietnam.

It's notable that the 2013 Mac Pro was the last Mac Pro Apple launched; the pro-grade desktop computer has not been updated since. Apple promised a big overhaul for 2019; if the NYT report is accurate, it's unlikely that it will be entirely made in the U.S.