I'm a fan of single transferable voting, but the claim that FPTP is responsible for America's politics does not seem well borne out by the evidence. As the Wikipedia article on Duverger's Law notes: "In practice, most countries with plurality voting have more than two parties." The USA is very much an outlier here. Even if there remained only two _dominant_ parties, a significant third party like the NDP in Canada, or the Liberal Democrats in the UK, would reshape congressional politics very significantly.