The majority of the US electorate is underinformed and/or misinformed.
The most popular cable news network is Fox News, which pushes straight-up falsehoods as propaganda for the right. That's not to say the left-wing networks are innocent, just that the most popular one is also the most dishonest. It has a wide reach and many voters get all of their news from only this network.
The right-wing party is completely bought out by the fossil fuel lobby, which has peddled the "global-warming-is-a-myth" narrative since the early 80's. Both the party and this lobby push that narrative through the right-wing media, which uninformed voters eat up, as the left-wing party has been completely demonized to them via that same media.
Those who trust these right-wing media outlets often do so on principle since these outlets are not "leftist" and the "left-wing media" is "out to get them". As a result, they often do not trust other media sources.
There is also the poisoning of the well that is filter bubbles on social media platforms (particularly Facebook) but I won't get into that as this comment is quite long already.
Hopefully this explains our problems to an extent. (I love explaining/ranting to non-Americans as they can empathize with my incredulity.)