not quite true - there are some regions that have a different set of AWS users / credentials. I can't remember what this is called off the top of my head.
These are different AWS partitions. They are completely separate from each other, requiring separate accounts and credentials.
There's one for China, one for the AWS government cloud, and there are also various private clouds (like the one hosting the CIA data). You can check their list in the JSON metadata that is used to build the AWS clients (e.g. https://github.com/aws/aws-sdk-go-v2/blob/1a7301b01cbf7e74e4... ).