The statement does not seem to be accurate.There are a lot of authors who contributed to making American literature unique.William Faulkner is one of them.He wrote taking into account the land of Mississipi.Using it as a setting for his works is an example of unique literature.In The Sound and the Fury he depics aristochratic people from the South of the country and the corruption of certain values they had.It is a local matter only interpreted though his eyes.
Ralph Waldo Emerson is another example.In his poem Good Bye he seems to be greeting his beloved land, with its coasts and hills; it is America he says good bye to.Hie essay writing topics are about America. Thake The Preacher , for instance.He criticises the work done , or not , in his homeland.."But the sentiment that pervades a nation, the nation must react upon...." it is incomparable America he talks about.
Topics such as religion, social organization around the land and it attributes, love and hate are developed in American Unique literature.The genres vary.There are poets , story tellers and essay writers.