All academic since it would never actually happen, but it seems like 3rd parties enjoy more success under parliamentary systems, and super unpopular governments can be tossed out more easily. Would things be any better?
I do think that a better electoral system could be a contributing factor towards a cultural shift. As it is now Americans cannot see a world which can be collectively improved because Americans have no clear path for that collective improvement. In theory a more parliamentary system would open up a path, and that could help more Americans see oh, actually maybe we CAN make the world a better place.
I think in practice the capital classes still wouldn’t let it happen but as it is now it is literally impossible to use electoralism for good, where in a parliamentary system it can still be extremely difficult but it isn’t necessarily impossible.
That implies Americans want to make the world a better place. The white American would rather die than see non-white American lives improved. They especially do not want non-Americans to benefit from better policies. The cruelty is the point and fascism is a death cult.
You’re more likely to see an emergence of additional far right parties than even the most milquetoast of reformers. We’d have the Tea Party and Alt-Right Party as official parties with their own politicians.