There has been a lot of publicity for the 1940 American Federal census which has just been made available (although not yet completely indexed) so I took a look to find someone who began their life in Sussex but had moved to America by 1940.
Charles John Coley married Sarah Ann Walder on the 23rd February 1879 in Brighton. Quite how Charles earned his income is not clear as he is variously recorded as a huckster, engineer, sailor and steam yacht engine driver! Charles and Sarah had a number of children including Amelia Hannah, Phillip Andrew, Attree John, Elsie Adelaide, Florence Minnie, Albert Kemp and Percy Maurice.
We are interested in Elsie; she was baptised in Chailey (as Alsie Adeline) on the 31st August 1884 and by the time she 18 years old she was working as a housemaid at the Belvedere Hotel in Brighton which is probably how she met her husband. On the 31st December 1908 Elsie married Theodor Nierhoff who was originally from Bochum in Germany and was now working as a waiter in England. Their only child Edward Kemp Nierhoff was born on the 21st September 1909 in Southwark, London.
Being German and living in England at the time of the First World War would not have been easy so Theodore and Elsie left for America with their young son.
I haven't traced Edward in the 1940 census yet but the 1930 census finds him with his parents in New York and working as a draughtsman.
By the time of the 1940 census Theodore and Elsie are living at 2213 East 18th Street in New York and next door to them is Elsie's sister Florence who is married to Robert Norman. Theodor is still working as a waiter whilst Moving to America appears to have been a good move for Elsie and Theodor, they retired to Clackamas in Oregon where Elsie lived to be 84 years (she died on the 22nd June 1970) and Theodor was 87 years old when he died on the 29th January 1972.