It is not a change but a three letter alternative imposed by ISO and unfortunately accepted by some idiots from Romania:
The two letters code is RO: after ISO 3166-1 alpha 2.
The three letters code is ROU: after ISO 3166-1 alpha 3.
The abbreviation is derived from the French name of the country: Roumanie.
Today the code is RO.
We haven't a special standardized abbreviation for Bucureşti; but you can write Buc. The car code is only B.
ROU is Romania, it was changed to ROU from ROM in 2007
Romania
The country abbreviated as ROU is Romania.
ROU is derived from Roumanie.
Originally called ROM, Romania changed its short designation to ROU when citizens noticed the similarity to the Roma people, known in some circles as Gypsies.
The cause is the Romanian government indifference and stupidity.
Cătălina Ponor Romania (ROU)
Romania
RO - Romania
Cătălina Ponor Romania (ROU)
Transylvania is part of Romania, and the currency in Romania is the Romanian Leu (abbreviation: RON).