Don't really have the courage
To stand where I must stand
Don't really have the temperament
To lend a helping hand
Don't really know who sent me
To raise my voice and say:
May the lights in The Land of Plenty
Shine on the truth some day
I don't know why I've come here
Knowing as I do
The idiom probably starts with the phrase “land of milk and honey” for Israel: 
 Exodus 3:7-8: Then the Lord said, “I have surely seen the affliction of my people who are in Egypt and have heard their cry because of their taskmasters. I know their sufferings, and I have come down to deliver them out of the hand of the Egyptians and to bring them up out of that land to a good and broad land, a land flowing with milk and honey, to the place of the Canaanites, the Hittites, the Amorites, the Perizzites, the Hivites, and the Jebusites. 
 “Land of plenty” has no single author but was famously used by Edgar Rice Burroughs in his 1918 novel “The Land That Time Forgot”: 
 “We haven’t one chance for life in a hundred thousand if we don’t find food and water upon Caprona. This water coming out of the cliff is not salt; but neither is it fit to drink, though each of us has drunk. It is fair to assume that inland the river is fed by pure streams, that there are fruits and herbs and game. Shall we lie out here and die of thirst and starvation with a land of plenty possibly only a few hundred yards away?” 
 The phrase “land of plenty” and “America” are closely connected today.  Merriam-Webster’s  uses the sentence “They thought of America as the land of plenty” to explain the verb “plenty”.
The Land of Plenty