Two-party dominance has been a feature of the American political scene since before the Civil War - that is, for most of its existence. I wouldn't call that "current short-term circumstances".
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.
Indeed; I just didn't want to get into the whole debate about whether the replacement of the Whigs with the GOP as the other dominant party was a meaningful change or not. But it's safe to argue that the present system, including the specific parties in question, has been around for >160 years now.
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.