The central point of this video was a surprise to me, since I’ve come to question if long-term global polarisation is actually happening at all, from watching the research over the past few years. However, from what I can tell the sources for this video don’t really settle the matter.
It’s well supported for the US case, but the first source on the international aspect actually argues at length the US situation is unique. There’s other reasons to think it’s not actually happening the same way everywhere; European and American populism has entirely different demographic dynamics, for example. This might be a case of Kurzgesagt editorialising a bit.
If they’re right, that sucks, because there’s no way people are going to stop engaging with each other on big platforms.