There is a well-known saying:
Two nations separated by a common language
. However, this phrase doesn't seem to have been positively recorded in this form by anyone. In The Canterville Ghost Oscar Wilde wrote:
We have really everything in common with America nowadays except, of course, language
In a 1951 book of quotations, and without attributing a source, George Bernard Shaw was credited with saying:
England and America are two countries separated by the same language
Even Dylan Thomas had his say in a radio talk in the early 50s:
[European writers and scholars in America are] up against the barrier of a common language
But where the original phrase came from, nobody knows, and it is probably simply incorrectly quoted.