Very odd title. Apple samsung and google also sell phones outside the us and the chinese manufacturers mentioned probably sell quite a lot of phones in the us.

The article begins by implying tech companies want thin phones. Which while not false is not entirely true either.

Tldr the cheaper chinese companies have been replacing graphite with silicon in the batteries to improve capacity at the expense of longevity. It's a new technology and it's obvious why the large companies would avoid it for now.

One interesting fact is that one practical limit for battery capacity is... Regulations! Any battery over ~ 5,400mAh would be classified as hazardous and cost more to ship, at least to eu.