After some testing I noticed the Choropleth Map expects ISO codes for countries and US states. Oddly enough, the US states map works with iso2c codes, while the countries map expects iso3c codes.
Would it be possible to have the Choropleth countries map work with iso2c codes automatically as well? And/or to document the expected input format? I didn’t find anything choropleth related on http://docs.exploratory.io/