Democracy Ranking has the USA ranked at 15th in the world, just behind Australia, Canada and the UK, and ahead of France.
One might note that this little cluster of long-term democracies at ranks 12-16 includes those that retain majoritarian electoral systems for at least their first (or sole elected) chamber. I will leave it to others to determine whether that is causal or coincidence, while noting that among long-term democracies, two PR (or mostly so) countries rank a good deal lower: Israel and Italy.* These just happen to be every anti-PR advocate’s favorite cases, notwithstanding that the top eleven are all long-term democracies using PR (including New Zealand, PR since 1996, at rank 8).
Japan, the other long-term, developed-country democracy with a non-PR electoral system, ranks at number 20. I know, correlation is not causation. But the correlation is noteworthy!
The full dataset can be downloaded from the linked page.
* Italy has not used a fully proportional system since 1992. After a period of mixed-member majoritarian from 1994 to 2001, it switched to a bonus-adjusted PR system that guarantees a majority of seats in the first chamber to the party or alliance of parties that gets a nationwide plurality. So any arguments about PR and flaws in Italian democracy are seriously out of date. Yet it remains true, especially since the 2005 reform, that Italy’s electoral system makes it easy for very small parties to gain representation.