The leaderboard used to have country and city based sorting up to ~6 months ago, James had to disable it to get some other site-wide changes working. At least, I believe that is the last time we had a working version. I hope that implies that it should be “easy” to readd the functionality.
What I used to do years ago before that now-disabled country-count/city-count leaderboard existed, was to sample the top x striders from the regular global leaderboard to see how many countries/cities they had. It doesn’t give you an exact rank, but it gives you an idea at least of how you compare. (I think I eventually wrote a script to do it for me as well, but I don’t have that at the ready to run for you).
I don’t have any of the old data saved, but I can tell you I don’t think I was top 100 based on cities and I have currently: 29 countries, 75 regions, 571 cities.