Aunt Agatha sees off Cyril Bassington-Bassington from Southampton Docks. The Ocean Terminal Building was not opened until 1950, about 20 years after this story was set. Also, he apparently departs on a Cunard liner, which has become a French one by the time he arrives in New York.
On the map of the USA showing the path of Cyril's touring show, they get to Tallahassee, Florida and the next town listed is "Pensacola, Alabama". Pensacola is in Florida.