@freemo @bonifartius No, because FPTP only applies to the top ticket in America (i.e. the Electoral College). Down-ballot, third parties are vastly more competitive.
In a parliamentary system, the parliament usually chooses the head of state, not the general populace. So, since the population isn't forced into coalitions for the top of the ticket, they're able to vote more locally for their MP who then votes for the HoS. That allows more parties and gradual transitions and power shifts.