I couldn't find anything by the theatre critic and H. L. Mencken collaborator, George Nathan, in the Librivox catalogue. A couple of suggestions:
"Europe After 8:15" by Mencken, H. L. ; Nathan, George Jean, 1882-1958 and Wright, Willard Huntington, 1888-1939;
https://archive.org/details/europeafter00menc
It seems to be an idiosyncratic, satirical treatment of the views expressed by imaginary American visitors to Vienna, Munich, Berlin, London and Paris. It was published in the ominous year of 1914.
Other books by George Jean Nathan at Gutenberg:
http://www.gutenberg.org/files/27660/27660-h/27660-h.htm
Nathan was a famous theatre critic and a clever, stylish writer. I think he deserves to be read by a American.
Best,
Barbara