Australia has had ranked choice voting for decades. Wikipedia describes their system as a “mild” two-party system. https://en.m.wikipedia.org/wiki/List_of_political_parties_in_Australia
I don’t see any reason the US would have a different outcome. But I believe transitioning from our current “hard” two-party system to a “mild” one would be a huge positive.
I think no more than two parties would dominate, even in a ranked choice system. But they would evolve more representatively: party platforms are shaped by issue polling, with the ballot box being both the ultimate poll but also obscure on what exactly the detailed driving issues are.
Ranked choice voting would give single-issue parties a real seat at the ballot box, and enable the two big parties to more accurately adjust their platforms to target voters who first-choiced a little party and second-choiced one of the big ones.
The Netherlands has party-list proportional representation. https://en.m.wikipedia.org/wiki/Party-list_proportional_representation
Instant run-off / ranked choice voting is a different system, and where implemented I’m not aware of it leading to many parties. I believe it will make the two parties better, which is still a good and beneficial outcome.