Cataluña is a historical region - it is not, has never been, and is pretty unlikely to ever be, a country like, say, Scotland.
An interesting comparison... I would be interested to know your definition of country.
Scotland is part of Great Britain, and thus part of the United Kingdom of Great Britain and (Northern) Ireland.
Following the logic of some on here (states v countries) Chess.com should remove the flags of the EU28 member states and replace them with the EU flag...