"Bitcoin mining" is better thought of in 2 parts:

1. hashing

2. block template production

The hashing is very decentralized, both in terms of it's locations globally but also who and from what nations control it.

The block template production, on the other hand, has become extremely centralized. This is a complicated subject and you can search youtube for podcasts with The Bitcoin Mechanic to learn more.

Also you can look at Ocean mining and how they are working to fix this problem.