One could use the free OpenStreetMap Nominatim service (but be aware of the usage policy!).
For affiliations/addresses like
British Museum, Great Russell St, London
in a column you could add a column by fetching urls with a throttle of 1000 ms (because of the policy) with
"https://nominatim.openstreetmap.org/search.php?q=" + escape(value, "url") + "&format=jsonv2&limit=1&addressdetails=1&email=YOUR_MAIL_ADDRESS"
and than add another column by parsing the JSON response for the country value with
value.parseJson()[0]["address"]["country"]