It is expected that the value for countryCode will be blank when you retrieve it as
this field is generally used for filters. According to the
documentation, it is used as a hint or suggestion when you are doing your filtering. For example, you specified
CountryCode EQUALS 'US' when calling the API. This means that the results returned by the API is filtered by the countryCode, specifically if it is equal to 'US'.
Hope this helps.