.The way my son described it to me, was that they put you in 'groups', 'silos', 'buckets'. They (the social platforms) find what you like and then target you with everything related to that. Are you a 'religious' person, they surround you with everything religious until you think EVERYONE is a religious person. Are you a 'racist'. They inundate you with everything that would be considered racist and after awhile you think EVERYONE is racist. Are you a 'Communist', ... 'Gun Lover', ... 'Social Conservative', ... the List goes on.
The eventual effect is that you are in your 'own world', unconnected with actual everyday people that are all around you. It divides the Country. There's no real communication between one 'silo' and the next. From what my son tells me, it's a pretty good descriptor of why the Country is like it is.
Yes, algorithms, the new evil, the new spies.