Thanks to Elizabeth Hummel on the Ballad-L list, we now know that Roisin White learned the song from Frank Harte; where he got it remains to be seen.

There is another edition of Pat in America at the Bodleian, which I missed earlier as it didn't specify a tune; it was printed by T. Taylor of Spitalfields, London, "between 1859 and 1899":

Pat in America

The Happy Land of Canaan spawned a whole series of songs, apparently dealing mainly with the American Civil War, and very much in the Minstrel Show style. The earliest certain date I've found is 1860, and both Canaan and Erin show up in the same time-frame (the latter only in Irish and English broadsides so far), so I wouldn't like to guess at which was the earlier; though Canaan seems perhaps to have the edge at the moment. Here is the tune for the set at the  Lester Levy Sheet Music Collection. It's recognisably a close relative of O J Abbott's tune, but a great deal faster.


X:2
T:The Happy Land of Canaan
C:"William A. Wray of the Original Campbell Minstrels."
B:Sheetmusic. Campbell Publication: Cincinnati: John Church, Jr., 1860.
N:Levy Sheet Music Collection: Box 024 Item 032
N:Roud 7705
L:1/8
Q:1/4=100
M:2/4
K:F
F|F Hz/ c/ c/ c/ Hz/ A/|B3/4 A/4 F3/4 F/4 E3/2 c/|
w:White folks at-ten-tion a song I'll sing to you, 'Bout
c3/4 =B/4 c/ d/ _e G3/4 G/4|G/ F/ z z A/ B/|c/ c/ c/ c/ c c3/4 A/4|
w:matters and things that we are en-gag-ing, I will tell you in these times In a
B/ A/ G/ F/ (E/ C/) F/ G/|c c/ A/ G/ c/ B/ G/|
w:few and sim-ple rhymes,_ Caze I'm rite from de hap-py land of
F2 F2|"Chorus" F f f2|c c/ d/ _e3/2 E/|
w:Can-nan. Oh, oh, oh, ae. ae. ae, ah, the
E E/ E/ e/ e/ e/ d/|d/ c3/2 z A|c/ c/ c/ c/ c/ c/ A/ A/|
w:day ob de pen-ti-cost am com-ing, So neb-ber mind de wed-der, But get
B/ A/ G/ F/ E/ C/ F/ G/|A A/ F/ G/ c/ B/ G/|F2 F|]
w:ob-er doub-le troub-le, Caze I'm rite from de hap-py land of Can-nan.

Some of the Civil War buffs round here may be able to provide more information on Canaan and its various permutations. (There is a Trinidadian Spiritual Baptist song by the same name, but it appears to be entirely unrelated.)