It seems that there have been changes to the structure of the V2 version of the RestCountries API. Don´t know when it changed but can this be the issue?
The structure of V2 has been reverted to its original form from the Original Project to maintain compatibility.
You might be right. The url: http://restcountries.com/v2/all did always give all the countries back in a json array. Now it doesnt anymore. It even says so in the readme…