https://www.chess.com/awards/anathanatoid/passport
A Better Way to Get Opponents Country from api.chess.com

You can use the https://api.chess.com/pub/player/{username} endpoint, 'country' tag.

@Guendulain - thanks, but, to be clear, that is what I'm trying to avoid because it would be 30,000 API requests.

@anathanatoid The only way to fulfill your request is to ask country for each of your opponents. I do not see the other way to perform your request.
I am building a map of countries I've played opponents from. I have a rather extensive history (30,000 games) and can get the list of games easily enough, but to get the country of the opponents it seems I have to make an individual request, per player, to get it. Gak.
I thought about using the "country players" endpoint (https://api.chess.com/pub/country/{iso}/players) to just fetch as many players as possible, but that seems pretty idiotic. Any other suggestions?