USA has failed.
Britain is a mess.
India the world's largest is a failure.
Turkey has gone autocratic.
The US has been always been reluctant democracy(vis a vis the Electoral College). The intent may have been to have 50 Presidential elections, and for the majority of history, this also reflected popular will.
But since 2000, it's fairly obvious a Republican can no longer win the popular vote. They have had to eke out minority victories relying on flaws in the EC. Yet demographic changes are closing out even that avenue. This leaves more openly anti-democractic means(congress reversing outcomes based on gerrymandered state legislatures) as their only viable means of capturing state power.
The GOP, even before Trump, has generally struggled with anti-democratic sentiments. They make a big deal of founders and their fear of majority rule(which they wrongly interpret as East and West coasts). Merits aside, the GOP is open to minority rule and may increasingly see it as the only desirable option.
So America could become a democratic autocracy for while, until demographic forces tip the scales. That could ultimately lead to peaceful secessions or a bloody civil war.
I don't know much about Britain, but it seems to be a more robust democracy IMO. They may elect crazies, but it will still reflect the will of the majority. Their problem seems simpler on the surface.
India has surprisingly done well for a country with over a billion souls. They will remain democratic just because any other options are recipe for unmitigated disaster. They are not China.
Turkey is culturally a strongman's playground. Democracy is just a weird concept in some of these cultures.