I think that Edo was centralized to a similar degree as medieval England - not that it necessarily had a central bureaucracy that we'd associate with a modern s

I think that Edo was centralized to a similar degree as medieval England - not that it necessarily had a central bureaucracy that we'd associate with a modern state (although I believe in actuality that the samurai-staffed bureaucracy in Edo was on a similar level to contemporary states in Europe, if not as sophisticated as China), but that it was never under any serious doubt that one government had legitimacy to rule over the entire country. There were no daimyo, as far as I know, that ruled territories that the Edo government struggled to control, after the foundation of the Tokugawa Shogunate. By contrast, France had powerful independent duchies until at least the 1500s.