Lack of ranked choice voting and reference of the electoral college/gerrymandering force rational progressives to vote with the main liberal-ish party to avoid the alternative - which, even on its best days, is a fate exponentially worse and more destructive by every measure.
Would you mind explaining how introducing ranked choice voting would substantially help smaller/additional political parties? I always find it confusing how much Americans focus on the presidency and ranked choice voting when it comes to breaking the party duopoly. At the end of the day, there is only a single president and he/she will probably always come from one of the largest parties. The presidency somewhat inherently limits the influence of smaller parties.
What I would focus on, if I wanted to increase the number of political parties in the US, is the House of Representatives. If proportional representation (e.g. biproportional appointment, party lists, MMP, ...) was introduced there, it would allow smaller parties to hold real power. (With biproportional appointment, the seats are distributed according to party voter share while also ensuring regional representation). Do you know why this hardly ever comes up in the context of the US?
The crux is that a first-past-the-post voting system incentivizes voting for one of the two big parties. Voting third party is equivalent to voting against your preference of the top two. There's a bunch of really neat voting systems that avoid this problem handily.
I would argue that any majoritarian electoral system (winner-takes-all), including ranked choice, incentivizes large parties. There is some nuance between them, but I don't think that ranked choice can fundamentally solve that issue. Sure, you can enter a protest vote, but will it really change anything? I think that parties need realistic changes at gaining (some) power in order to be viable in the long term.
Seeing larger third party percentages regularly would be important - bit by bit and without threatening election of the lesser of two evils in the interim, could lead to exponential growth until that 3rd ventually competes as a valid 3rd party