There has also been a shift in the focus of politics away from economic policy and the running of government services (as was very much the case in the UK up to the 1980s) to social issues as a result of a centrist consensus on what were important issues - disagreement about them is now purely theoretical and off the table in terms of what might actually change.
It think the problem has also been inadvertently illustrated by people in the comments discussing specific American culture war issues with a great deal of anger.
An aspect of this is the lack of willingness to compromise. Take abortion. It is much less of an issue in most of Europe because it is allowed, but with short term limits. It means many of the arguments for it are not relevant, but it also undermines many of the arguments against it because of lack of functioning brain tissue, or the state of development comparable to a premature baby. Anglophone countries are much more all or nothing - long term limits or not allow at all.
We also do not (even in the UK) have the American alignment of party politics with social issues. Can you imagine the Republicans being the party that allowed same sex marriage?
I think the moving of discussion online has primed people to be more aggressive about their views in general. I was thinking the other day about the people I know IRL who have blocked me on FB: my ex, a friend of hers, one of my ex's sisters (emigrated to the US and is a stereotype Trump supporter, stolen election theory etc.), a creationist (also my ex's sister, a nice person who keeps in touch with me, but does not like my comments on her FB posts), and a remainer/rejoiner.
