I think that's the answer. In order for a country to cut itself off effectively enough, it has to be (a) huge enough to replicate any service its citizens migh

I think that's the answer. In order for a country to cut itself off effectively enough, it has to be (a) huge enough to replicate any service its citizens might want that is found elsewhere and (b) authoritarian enough to crush/jail/imprison/ostracize them for circumventing it. So far even Russia hasn't managed both. I don't think any country but China can pull it off, so we're looking at worst case a Real Internet and a ChinaNet. The only other countries that will succeed will be backwater countries dooming themselves to perpetual backwater status (I can name a few but won't).