“The sane world” is, to be fair, a pretty exclusive club.

Maps with pretty colours and lists:
https://en.wikipedia.org/wiki/The_Economist_Democracy_Index ² https://en.wikipedia.org/wiki/Effective_number_of_parties#Effective_number_of_parties_by_country https://en.wikipedia.org/wiki/Gini_coefficient

Cross-reference with the maps and lists for proportional representation:
https://en.wikipedia.org/wiki/Proportional_representation#List_of_countries_using_proportional_representation

Many of the European states, which tend to use proportional representation, are doing quite well.

According to an aside on Wikipedia, technically most countries never used FPTP in the first place, rather than having “moved on” from it. “Its use extended to British colonies […] mostly in the English-speaking world”. Of those, however, some have indeed “abandoned it in favour of other electoral systems”.

Proportional representation has been tried and tested since at least “its first national use in Denmark in 1855”.¹

A major black mark on its history might arguably be the fact that it contributed to the instability of the Weimar Republic by creating too many parties competing for power— Though, that was only a problem because of the generally disastrous state of inter-war Germany (reparations, debts, loss of industrial zones, restrictions on their military, Treaty of Versailles, fall of the Empire, etc.).

In general, proportional representation has worked out pretty well for the countries that use it, though. It doesn’t magically fix everything, but the US’s two parties currently clearly aren’t working.

¹ (Side note: Danish civil history is really cool! Used to be Vikings, lost their imperial ambitions and mellowed out, democratized willingly, saved nearly all their Jewish people and even sorted preserved their democracy through WWII, then went fully Nordic model, and now have neat randomly sampled citizen’s assemblies that are probably how democracy really should be done.)

² (The US had been hovering barely above the threshold between “Full Democracy” and “Flawed Democracy” for years, based on the EIU’s ranking criteria. It finally crossed the threshold in 2016, and has been falling alarmingly quickly ever since.)