There are stacks of US companies that have made a significant entry into China:

  * Coke
  * Starbucks (the largest one in the world is currently in Shanghai)
  * KFC
  * McDonalds
  * Pizza Hut
  * Domino's Pizza
  * US movies regularly make as much money in China as they do in the US.
  * General Motors sells more cars in China than in the US.

Have they put in place limits that they are legally allowed to put in place based in WTO rules? Yes.

Part of the reason that AWS has two separate companies is because China, the US & the EU have laws like the CLOUD Act, GDPR and CDPR. It is easier to keep all companies seperate or at least siloed which is what most large companies do.