Nonetheless, what are your thoughts about this?
It would survive. And at this point it is very unlikely that ALL countries would ban it. If anything, its the minority of oppressive regimes that do. But still, bitcoin was designed to resist this from the start. Sure hashrate and price would fluctuate, but it would find its place and things would continue as usual: 1 block every 10 minutes.
If it became draconian, perhaps more/better obfuscation would be needed (like the Tor project). I'm sure the developer's community would respond to the challenge and go around any censorship.