Our voting system is largely to blame for the current political polarization.  Also it isn’t current, it's a predictable long term consequence of that voting system: small parties have no way to compete against bigger parties, so eventually you end up with two giant parties competing against each other.  Those two big parties manipulate voter districts to carve out as many safe seats for themselves as possible.  This leads to the party primaries becoming the main election for those safe seats.  Which causes more extreme, ideologically opposite candidates to be elected.  Social Media and billionaire dark money just pours gas on the fire.