Yet in PR countries, small parties are often unfairly influential, as they often act as tie breakers when it comes to forming coalitions. Personally, of the two systems, FPTP seems to me far better: why should mainstream parties have to incorporate policies into their platform that just a tiny fraction of the population agree with, just to form a coalition?
Also, the Lib Dems currently have 10% of the seats in Parliament. 2–3% of the seats wouldn’t be a good year for them, it would be a disaster! In the local elections, they currently have 25% of the councils, ahead of 21% for Labour. The Gerrymandering is there (and affects the Tories as much as the Lib Dems), but it isn’t as bad as you’re claiming.
In 1983, with 25.4% of the vote, the UK Lib Dems got 3.5% of the seats. In 1987, with 22.6% vote, they got 3.4% seats. In 1992, with 17.8% vote, they got 3.1% of seats.
Since then, they have managed to climb to 7%, 7.9% and 9.6%. they have received these seats, by a strategy of targeting resources only at vulnerable seats which may be won. In effect this is a strategy of turning themselves into a regional not a national party.
They have also benefited from one or other major party losing votes, so that the gerrymandering effect was minimised. However, they have never received even half the seats that their vote would imply. in the last election they got 22.1% of the vote, but only 9.6% of seats. And that was by targeting vulnerable seats, as above.
I believe you are mistaken: America has supported and continues to support many different types of democracy, both Presidential and Parliamentary, single chamber and multiple chamber. And constitutional monarchies too. Germany, Italy, Spain, Thailand, Israel, Egypt, etc.
And winner-take-all has two stand-out benefits at all levels: it maintains the direct link between the elector and the elected, and strongly mitigates against party hacks.
As for 3rd parties and their getting squeezed, they may not get power, but they do get influence, and they do change the results. Further, and specific to the Lib Dems, here in Luton, it’s the Conservatives that are the third, squeezed, party. For the Council elections, they didn’t even bother standing in my ward.