Hi Bernard.
A lot of this would of course depend on the definition of an Aircraft Carrier. In 1913 several merchant ships were converted to "Seaplane Carriers" but these could only carry the seaplanes to where they were needed, lower them into the sea where they would take of and land.
The first Launch from a British ship was on 10th January 1912 from a platform fitted over the front gun turret of HMS Africa moored in Chatham Harbour and the first launch from a ship under way was in May 1912 from a similar platform rigged on HMS Hibernia. Then in 1917 the front guns were removed from HMS Furious and a flat deck was fitted. After several launches Sqd Cdr Dunning RN managed to land on deck. This was particularly difficult as he had to fly around the ships superstucture and on his second attempt he lost his life. Soon after that "Furious went back in for refit and had a flat after deck fitted.
In May 1917 the "Conte Rosso" was launched in Scotland. Although built for the Italians the RN were quick to see the potential and commandeered the ship to convert as a "Carrier". Completed in October 1918 they had fitted a flat deck, renamed her HMS Argus and thus the worlds first "Flush Deck" carrier was born (Due to her appearance she was known as "The Ironing Board").
Then in 1918 plans were laid down for what has become the norm in carrier design. Completed in 1924 HMS Hermes became the worlds first conventional carrier, with Flush deck, Starboard (right) Island superstructure, lifts and a through deck hangar.
By comparison the US Ship you mentioned was the USS Langley (CV1) which was launched as a similar design to "Argus" in 1919, nearly two years later. Their first conventional carrier was USS Lexington (CV2) completed in 1927, three years after "Hermes".
Sorry to be so long winded with the answer but it is the only way to explain the answer. .
Incedently, I was station at NAS Pensacola for a short while whilst serving in the USA along with NAS Jacksonville and NAS Cecil Field. What a great time I had over there. CHOCKS
