Most of sub-saharan Africa has slow and expensive internet. I would guess there is 1 billion people who will have access to the internet via mobile tower with starlink & competitors backhaul in a few years. This is enormous.
There's nothing in the landscape that prevents Africa from running fiber to every house like Eastern Europe has been proven to be capable of. In fact, a lot of infrastructure is already there. Geopolitical instability, poverty and instability of the power grid makes it very unattractive to build data centers in the continent and that's what's forcing ISPs to use expensive cables to access most websites, driving up the cost and reducing the speed.
This problem can be partially mitigated by using StarLink instead of oceanic cables, but I don't imagine their system will be able to replace the fiber optics that carry most large volumes of data between governments. StarLink is fast, but still depends on ground stations for decent speed internet access. Collecting internet traffic for one entire continent on another isn't feasible in the plans I've seen.
StarLink will reduce latency and improve coverage for customers already using satellite internet connections. African people can already use those if they have the means to afford it, yet many African cities have dial-up or slower internet access because of the lack of resources.
Has any nation ever successfully outlawed satellite reception? The roofs of buildings even in nations like Iran and KSA are studded with dishes.
Musk has already admitted that providing satellite services to countries like China can become a problem [3]. Countries that don't want StarLink and don't have the capabilities to take out LEO satellites might start to team up with China, Russia and other countries that do to protect their sovereignty.
Of course there's no way to prevent hardware that someone managed to sneak in from connecting to the satellites. Those devices will all need to come from the black market though, severely limiting the reach and future business StarLink might have in such a country.
[1]: http://www.gard.no/web/updates/content/26690148/ban-on-use-o...
[2]: https://en.wikipedia.org/wiki/Satellite_phone#Countries_with...
[3]: https://www.businessinsider.com/spacex-internet-satellite-co...