[eevmanu]

  cr=country<two letter>

I have a "kind" of similar need and use *cr* query param based on *ISO 3166-1 alpha-2* [1] to force official language when i want to narrow the search on a specific country (as example when I want to search for english, I use *cr=countryUS*)

[1] https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2

p.s.: YMMV, sometimes works, sometimes it doesn't, most of the time works but there is no determinism