[ver_ture]

The two party system does not affect this discussion. Facebook's algos will show you more and more $x content if you've liked $x or subscribed to it, and never show you $y content since you'd probably not like and engage with $y. Doesn't matter how many parties/topics/underlyingIssues there are.

If FB were neutral they would show you every FB post, millions per second whizzing past your screen, but they can't do this, they have to curate a wall for you to slowly scroll through and for most revenue, like, share, or comment on.

Therefore, to show you the most content that you will like, share, or comment on, they repeat the type ($x) you've already liked, creating the echo.

So no, it is not mostly a problem of the underlying issue of the two parties, this is entirely about how FB curates your wall and simply doesn't show you "the other party"/$y or anything deviant/$y of your likes.

Edit: changed political parties to variables to illustrate point.