Because the US presidential election is a winner-takes-all decision. A third party is mathematically useless. And to become a “winner” the other has to be displayed as “loser”. Division is build-in. I’d suggest you transform into a parliamentarian/multi-party democracy. This basically means a president as a head of state with only ceremonial value and no executive power.
Missing in that article is the heat capacity of ocean water and missing ice that reflects back a lot of heat. Marine life is already dying from the lack of oxygen. Almost half of our oxygen gets produced there. With added effect on acidity, salinity it also affects ocean currents. It’s not bad soon. It’s bad now.