[wenderen]

Collecting some of the points other posters made:

1. Languages don't always neatly map to country borders.

2. Linguistically diverse / multi-ethnic countries can have multiple official languages, and some of those official languages are spoken only in a geographical subset of the country.

3. Languages can be mutually intelligible. Urdu and Hindi are mutually intelligible and you can get by speaking Urdu in most parts of North India. The Balkan languages are largely mutually intelligible - correct me if I'm wrong.

Cute visualization, half-baked idea.

[Freak_NL]

3½. Just because you speak passable German, doesn't mean you can always understand the Swiss (even when they speak Swiss German!).

[BrandoElFollito]

Even if you speak native German, you will not understand a seizable part of Swiss who will be speaking their language (French, Italian, Romansh)