Not all RR were built in England, the company had a facility in Springfield Massachusetts. In 1919, after the First World War, Rolls-Royce recognised that the USA was the most important car market in the world. Americans bought more cars each year than the rest of the world combined.
From Automobile magazine and http://www.darkforce.com/royce/springfield.htm this website claims to be the unofficial and most comprehensive RR and Bentley website
