[gilbetron]

It isn't population density, since we used to discuss politics all the time until 2016. Family get togethers, work events, just friend hangouts, all of them would have active discussions and arguments surrounding politics. The Trump era changed all that. I don't know about India, but I think social media is what changed everything, and how it changed everything is more complex than many people think.

There are so many factors to it. The non-stop nature, the echo chamber effect, how it allows you to hear the thoughts of people you never would have heard before, but also, and maybe this is a big difference with India, that insane effort from Russia and China (and others) to maliciously engage with our social media with the sole goal of disruption of our culture and nation.

I'm in my 50s, and there was plenty of political discussion before 2016, much like the person from India in the OP describes. We used to have a close friend in our friend group and we would regularly tease each other over political issues, but also listen, and he was a staunt Obama-hater and subscribed to birther conspiracies. Two years into Trump and we stopped being friends, and I haven't talked to him since 2018.