The only problem is that RCV has basically bipartisan opposition in stronghold states. You see it being blocked in red southern states, but it also failed to pass in Massachusetts, which is as blue as they come.

RCV makes it likelier that the currently prevailing party ends up as the #2 vote on more people’s ballots (i.e. eliminating the need for “vote blue no matter who”) and that threatens their overall presence in government, so they do whatever they can to stall efforts to implement RCV.