Unless all the goats and sheep died out after the Sumerians left or that that the Sumerians used the term goat or sheep for an indigenous native American animal like a deer or buffalo then the receipt makes no sense.
Goats and sheep need to be protected from predators. Both wolves and indians were predators and also migratory scavengers. The sheep never stood a chance after the fall of Sumer ~1800 BC.
There is a third possibility, that the Sumerians brought theor own breedomg stock with them and had their own herds whichi later did not survive their absence.
I bet there is archaeological evidence of Sumerian settlement somewhere in America.Or else we would not have these cuneiform receipts.
Ground scanning radar anyone?
They could have identified native mountain goats as goats as we did and still do have mountain goats. I don’t know what they would have called a sheep, unless the hairy buffalo.