It's also very hard to change because both major parties benefit from the existing system and are protective of it, knowing full well that proportional representation would cost them a lot of votes. Republicans usually trot out the old "but small states!" canard, while Democrats are getting creative and claiming that IRV and RCV are racist because e.g. "majority voting may seem innocuous, but if the vote is racially polarized, “runoffs discriminate against Blacks because they are a minority of the voters.”"

Given that Congress has the final say on how federal elections are run, I find it rather unlikely that this is going to change anytime soon - at least, not as long as federal politics is consumed almost entirely by polarization and voting against rather than for.