I think FPTP ends up working out a lot different in the parliamentary context. The US only has 2 parties in Congress, despite FPTP. In terms of strength of 3r

I think FPTP ends up working out a lot different in the parliamentary context. The US only has 2 parties in Congress, despite FPTP. In terms of strength of 3rd parties, I'd say they are generally quite weak in the US system, somewhat stronger in a proportional representation parliamentary system, and potentially overpowered in a FPTP parliament like in the UK. Historically I believe the 2-party system in the US was pretty good at tamping down on extremism, but recently the 2 major parties have acquired too many extremists.