Yeah, it’s one of the very few advantages of the fact that their elections—even federal elections—are not actually standardised nationwide. States run them according to their own rules. Mostly this is a bad thing, but it does mean that one place can improve their system like this as an experiment, without needing to convince the entire country to do it at once.

So I think there are 2 states that do IRV currently. And there might be a few more places where IRV is used in non-congressional/presidential races.