Even while many people in the US might like the things a parliamentary system has to offer, there is no viable way to transition to one culturally. As much Americans hate how politics works presently, they hate the idea of replacing it even more. The socio-cultural hesitancy is real, paradoxical, and cannot be ignored.
Hm... Germany's system changed at least 3 times in the 20th century. France is on its Fifth Republic. Italy is a shitshow.
To me it seems that the oldest democracies (UK, US) are the most stable (even today!) and they're majority systems (first-past-the-post).
Only if you believe fake news media propaganda who equated "mostly peaceful protest" with "coup" (for real examples of a coup, look no further than Libya, Ukraine, or Myanmar; hint: it usually involves guns & people getting killed).
The worst case for representative democracy is literally Hitler. The second worst (you could argue that Hitler was a unique set of circumstances) is the dysfunctional German, Italian, or French states.
The best case is probably Switzerland (party proportions barely change, I assume because the power of parliament is diminished because of elements of direct democracy that Swiss practice).
What's the worst case for first-past-the-post democracy?
..cites two of the most important examples