I don't buy Apple products, and I know other Americans who don't. Surely fewer than 339,980,000 buy from Apple. Maybe 170,000,000.
How does it start? You are planning manufacturing for a new product and the general contractor for the new factory says 15% of the new building cost will be permitting paid to the city. Then the city wants yearly proprty taxes and if it's my state those taxes will be higher than what owner-residents pay. When it's done all the factory workers want enough compensation to cover your half of the SS and Medicare taxes, their half, and their state and federal income taxes. Oh and the EPA wants some more money expensive changes made. Finally OSHA has a surprise inspectionat your existing factory which just voted to unionize. Then a manufacturing provider comes to you and offers to handle all the manufacturing. You don't need to worry about safety, about unions, nor about emissions. So you buy from this manufacturing provider and your new product is built in China at a much lower cost. Your expenses go down so you sell your product for a little less so you can sell more, but still with a bigger margin than before. The stockholders get a great return and give you a raise. Everyone you report to is happy.
Now your competitors are at a disadvantage. They're selling less at a lower margin. Their stock is going down. The CEOs have to find a way to lower costs or be replaced.
That's just one piece of what's happening. Another is that there are 340 million people in the US, and a billion in China. Selling to China means a huge increase in the size of the market you can sell to. But the Chinese government is stopping you unless you start manufacturing your most advanced product there. Sure some proprietary manufacturing technology will leak to China, but the shareholders don't see that, they just see a billion potential customers.