regions.js

var regions = _.chain(originalData[year])
  .map()
  .first()
  .thru(function(object) {
    return object.total.letters;
  })
  .map(function(value, region){
    return project.i18n.getTexts('myI18nKey') + ' ' + region;
  })
  .value();

I don't think there's a need for the empty map and you can use .get('total.letters') instead of thru.