Feels more and more like we're at the end of an era when it comes to the internet.
Certainly it's possible (and perhaps likely!) that the EU and US will want to copycat this kind of law, but until that happens, I think your alarm is a bit of an overreaction.
EFF summary on Section 230: https://www.eff.org/issues/cda230
Are you suggesting that if the European Union were post-Westphalian that the UK wouldn't be able to leave? Not sure how that follows. That the EU is a post-Westphalian system is not a new idea.