Length of password is partially dependent on language (e.g German words tend to be longer on average). Also, many languages have their own diacritic characters

Length of password is partially dependent on language (e.g German words tend to be longer on average). Also, many languages have their own diacritic characters (å, ä, ö, etc.), which, when used in password, will be counted as "special characters" (because they do not match standard [a-zA-Z0-9] regexp). So yes, password safety is at least partially influenced by user's language.