And plenty of people, including myself, thought "this is so dystopian it couldn't possibly happen".
It did happen, and it's as bad as the doomsayers said it would be.
If you want to watch porn or view anything NSFW with websites that complied, I suppose you just start up NordVPN and select Chicago or something like that. Brits who watch porn are probably just watching more American themed porn now.
Otherwise, (some of) these websites are supposed to show you a digital verification screen with third party gateways. Usually using an ID card. I'd guess most people just installed VPNs.