It's amazing that you can't understand each other even if you're from the same country.
「同じ国なのに分からないって不思議」は英語で「It's amazing that you can't understand each other even if you're from the same country.」と言います。「不思議」は色んな翻訳があって「weird」、「strange」、「amazing」などですが、「amazing」(「すごい」に近い)のほうがふさわしいと思います。
スイスには四カ国語があると聞き、同じ国なのに分からないって不思議!
I heard that in Switzerland they have four languages, and It's amazing that some people can't understand each other even if you're from the same country.