Not sure what you mean by centralization. Nuclear power plants can be enormous or tiny. Typically in the past they’ve been built huge because that generated cheaper power. Does that answer your question or another topic?
Discussion
If we went nuclear, would there need to be a plant on every county, or a plant in every state? I've not researched this but I've never heard of a nuclear plant that could service like 10-100 homes which to me would be as decentralized as it gets unless you can have 1 per household.
You have fourth generation “micro” reactors as small as a few megawatts:
Or you can build gigantic ones where you might only new one or a few per state or anything in between. There’s no scientific limit in that regard. Just a societal choice.