Sorting by popularity in a country
Sorting by language works very good until a language is used in one country. In case of languages used in many countries, especially English, results are a mix from different countries. Users in the US, UK, India or New Zeland have a bit different interests, especially regarding American affairs.
Information about country of podcast origin is in a country domain like .co.uk, .in, .nz in RSS address.
Much more valuable is information about popularity in a country regardless podcast origin because it would include also what, mostly in English, is sufficiently universal to be interesting especially when there is no big choice of local podcasts. It would require analyzing of users location countries.