Death of 230 basically means every site with a presence in the US (hosted there, offices there, employees there, etc.) has to shut down all user generated content (comments, posts, blog, tweets, images), as the companies would be held immediately responsible for the content of each.
That is, if some guy on Twitter says “We should kill Biden”, then legally that would be considered Twitter itself making death threats about the president.
Basically it would turn the internet into a complete dystopia where 99% of sites are just static storefronts and the very few that had any UGC (comments, image uploads, etc.) would have extremely strict pre-moderation.