"Americay" is used in some 19th c. song sheets Both English and American printers). I don't know if this emphasis was by the song writers, or it was a pronunciation in normal conversation.
Here is a bit from a song sheet. I picked it because of its other common 'Irishisms':

Innocent Mike
(Tune- The Low-backed Car)

I am a wandering Irishman, they call me Innocent Mike,
I came across the Atlantic on a very stormy night,
I came across the Atlantic commonly called the say,
To roam in this dear country called swate Americay.
I'll be two months here the day I'm settled down all right,
Hould on and I'll tell you all about meself, poor innocent Mike.
(and four more verses)

America Singing: Nineteenth-Century Song Sheets, American Memory.
Printer G. W. Anderson, NY.