There is a way to be a cohesive society without being assholes to each other. The United States somehow managed that before - more or less. I would not blame "individualism" directly, but we ARE in a timeline where a lot of people strive to be the worst versions of themselves.
Sounds like a copout, but I do insist that many of modern ills can be traced directly to the cancer that is social media. Monetizing rage cannot end well.
Remove "social" from media. It's just media. Books, film, radio, TV, video games, social media.
Not all, but a good proportion of each of these forms of media.
I suspect that the US managed its cohesion by keeping everyone but white straight Christian protestant men far from cultural and political power. It's easy to be cohesive when everyone looks, acts and thinks like you, and when the white establishment controls the media and sets cultural norms. Not that I'm advocating for a return to this at all - there are examples outside of the US where multiculturalism works. It just seems to be the case that the US has never really been comfortable living by its principles.
And this is one part of society's ills that I will kind of blame on social media, although not in the way you and a lot of HN people intend. I think a lot of the strife in our modern society comes not from social media algorithms driving outrage so much as other groups simply being able to gain visibility as the centralized media establishment gave way to the far less centralized structure of the web. To people who have grown up their entire life with only rare, token (and often stereotyped) representation of other races, religions and orientations, equality can seem like oppression.
But I do think that blaming social media is kind of a copout, because the argument tends to be that people are being manipulated and controlled by an addiction or a form of mind control, as if they don't have agency or free will. A lot of the discourse around social media right now seems to use the same hyperbole that one might have seen during the Satanic Panic, or any number of previous social panics. But I don't think social media is the problem per se (nor do I think regulating social media would be an effective solution.) I think the problem is what social media exposes in society - exposes, not creates. That's a far more difficult problem to solve because it means reconciling with some deeply systemic issues that a lot of people still don't even want to admit exist.