They're going to switch again within the next two years, by my estimate. It'll be big, traditionalist sects (Catholic, Mormon, etc) on the right and cannabis on the left.
This leads to the two parties only ever being in an adversarial relationship.
In other systems, sometime you get to make a majority government with other parties. This differi means that in mutti-party systems the "party line" is "these guys are ok, and reasonable" every once in a while.
Not so in the two party system, where the winner-takes-all perpetual adversarial relationship generates a constant steam of "the others suck, are dumb, evil and want to destroy the country"
The other side has...politicians who are too beholden to corporations to fight as hard as they should for progressive policies.
If you genuinely think that the American left is just as bad as the American right, then either you really haven't been paying attention, or...I guess you think the Nazis had a point or something?