[ketralnis]

Unless you have different pricing per country or something orthogonal to language, I'm sure than a speaker of Canadian French can figure out that clicking the French flag may help them understand this page better. It's a common enough idiom on the web.

[_delirium]

I think in the case of more than one country per language, you're right, just picking a big and/or well-known country as "representative" is fine: French flag for French, US or UK flag for English, German flag for German.

The bigger problem is the other situation, of more than one language per country. India has ~13 languages with >10m native speakers, and using the Indian flag for all of them would be pretty confusing. You could pick state flags (e.g. the flag of Gujarat to represent Gujarati), but that can be a politically tricky issue. In some cases choosing a representative flag for a language has even stronger political overtones, like using the flag of the Kurdistan independence movement to represent the Kurdish language. Plus, it's not always that clear which flag to pick, and user recognition may not be as high as in the French-flag-for-French case.