Earlier quoted context omitted.
That wouldn't do anything, since CF's CDN connects to the backends directly. As such, any CF server not within the nation in question would effectively be a circumvention tool.
These are BGP blocks, right? If Cloudflare's ISP doesn't have a route to the system in question, then it can't proxy the site anymore. Maybe Cloudflare has an Ethernet cable between the server in question and itself, but that seems unlikely to me. There is probably some ISP in the middle that will play ball, right?
I'd imagine that CF's first act would be to remove any of the "offending" content from the country, at which point BGP blocking would no longer do anything.