I think you listed most of the important issues.

From a company standpoint, being fully-remote is already a non-conservative approach and minimizing risks by only hiring in a certain region makes sense. Your talent pool will stop being a constraint anyways so why add more complexity.

One more thing I'll add to this list is culture and language. Even if on paper everyone speaks English, communication is much easier when everyone speaks the same accent / dialect / local non-EN language.