What is the , average, size of an Americans mans 3rd appendage?

There's not really a good answer. There are have been studies performed that seem to indicate the average size is between 5"-6". However, these studies would only constitute 1,000 to 5,000 men overall. A very small percentage of the global population. I'm more inclined to believe the average is between 4"-6" overall with anything below 4" being below average and anything above 6" being above average. Regardless, there is no entirely accurate information as the amount of study is too sparse.