In this house, LRMs in Australia, Israel and USA plus plenty in Europe.
Shorter brevets in Australia, Belgium, Canada, France, Germany, Greece, India, Ireland, Israel, Italy, Netherlands, Portugal, Spain and Thailand. Not many instances of multiple brevets in most of those countries.
You might do better looking at countries that you want to visit anyway (visit friends or a holiday) and also have long brevets. Then find out whether the roads in those regions would be fun to ride.
https://www.randonneursmondiaux.org/51-Calendar_2020.html for 1200s and the ACP website for worldwide 1000 BRMs.
Countries that use the roman alphabet are relatively easy to cope with. Alternative alphabets are tougher to read/ translate/ follow on maps for this little, black duck but YMMV. Most LRM organisers go out of their way to assist foreign entrants. Friends (and I) have had local riders escort them around brevets in parts of Asia where few speak English.
Ivo has probably ridden randonnees in more countries than any other YACFer but also he knows more languages than anybody I know.
The LRM President, Mark Thomas, has ridden 60 x 1200s in lots of countries but he rarely lurks on YACF.