What is the earliest mention of an "American accent"?

Do we have any idea how quickly the American colonists (specifically those British colonists living in what would later become the United States, but I'd be curious about French and Spanish colonists in their respective areas as well) developed an accent that was distinctly non-European? What is the earliest mention of someone "sounding American," or speaking in a way that they clearly came from the colonies?

Solution 1:

It seems that the popular distinction between American and British speech occurred at least as early as 1735 when Francis Moore observed:

It stands upon the flat of a Hill; the Bank of the River (which they in barbarous English call a bluff) is steep

Source:

• The Origins and Development of the English Language - Algeo and Butcher

Solution 2:

The earliest mention of a specific American (non-European) accent I can find is from 1783. More specifically the accent described seems to be Virginian.

"...a clergyman of Virginia assured me very seriously, that the English of that province was the best in the world; and assigned the same reason in favour of the Virginian pronunciation. /.../
It is true, the North-American English accent is not so animated as that of Middlesex, and the adjoining counties; but it it very perceptible notwithstanding." James Beattie, Dissertations Moral and Critical.London 1783.