Though it may surprise, I don’t think the United States “needs” a multiparty system. There are reasons to think it already has many trappings of one. My audience for the phrase “more parties” was academic.
I am writing this now, in part, due to news of Jane Goodall’s passing. That got me wondering if she’d had a faculty position when she discovered gorillas using tools, or if that discovery led to one. According to Wikipedia, the evolution scholar Louis Leakey did not like it. I quote: “We must now redefine man, redefine tool, or accept chimpanzees as human!”
The intellectual situation with respect to electoral reform in the 2010s was similarly polarized. On one side were reformers with a stripped-down version of Duverger’s law. On the other were academic partisans who refused to entertain the issue, partly from annoyance at being told how to think about politics. (For that, I don’t blame them.) Others in the ideas business had to choose between these camps.
Meanwhile, reforms were happening more frequently in cities and becoming salient in state politics. It was getting harder to claim, as Mahmoud Ahmadinejad once did on a different topic, that we don't have electoral systems in America. Not all held that view, of course. “This issue isn’t going away soon,” someone told me as far back as 2010.
The phrase “more parties” was my effort to propose new terms of debate. If this is happening anyway, I reasoned, let’s interrogate the design principles. “Multiparty reforms” can be built to accommodate multiparty competition we might or might not get. Or they can be built to create a free-for-all.
One can get more parties with or without electoral reform. We see this now in the United Kingdom, where first-past-the-post is not containing fragmentation, and in several American cities, where socialists are entering government as such. Similarly, one can get electoral reform without getting more parties. At one point, maybe 2020, I compared the lists of Green and Libertarian officeholders to the list of cities with instant runoff and found almost no overlap. That may have changed, but I’d be surprised if rules were causing it more than the state of the party system.
In short, “more parties” does not mean we should have that. It means we should be thinking differently about what is happening anyway.