I actually think ranked choice voting would destroy our relatively successful third party here in Canada (the NDP).

Essentially when you survey voters you'd find that there's three voting blocs:

a) First choice Conservative, Second choice Liberal

b) First choice Liberal, Second choice NDP

c) First choice NDP, Second choice Liberal

Given this, ranked voting would probably just produce permanent majorities for the Liberals, and wipe out the NDP almost entirely. The Liberals are the first or second choice for most voters.

I'm not sure why 'progressive' voters here in Canada often seem to prefer this voting methodology when advocating reform. Experience in Australia should show them what happens, where both major parties are now pretty close to the right and left wing options are basically off the table.

I'm not the only person who thinks this. When the Liberal gov't tried to push ranked ballots through a few years ago analysts in the NDP clearly saw this as a threat, and did everything they could to stop it (along with the Conservatives), seeing it as a nakedly cynical attempt to ensure nearly permanent Liberal majorities.

I would far, far prefer a mixed-member-proportional system like in Germany.

And so, yeah, I agree I don't think in the US it would do anything. The same forces of conformity towards the right would still happen. Effectively the US already has a kind of ranking choice through its primary system. The two parties shift and "become" representative of whatever plurality can capture and win the primary.