In theory, but is that actually the case today? I couldn't find any information about the current state of federation for Bluesky.

Contrast this with Mastodon which already has a vibrant federated ecosystem.

Yes, it is the case today. Its not a huge proportion, but there are thousands on external servers, and we recently had a nice sized migration to blacksky

If it is decentralized then a ban in a US state would have no impact. Did not know about blacksky though. That is at least -some- progress.