Well, jtgd is close. The joke, explaining the difference between being involved and being committed, originated on Dick Gregory's 1961 album "In Living Black and White."
It followed one about the difference between the US and Israel -- "Here we have ham-and-eggeries that are fronts for bookie joints; in Israel, they have bookie joints that are fronts for ham-and-eggeries."
And the US and South Africa -- "At the battle of Bunker Hill, it was 'Don't fire until you see the whites of their eyes.' At the battle of Leopoldville, it was 'Don't fire until you see the whites.'"
Before he became purely political, Gregory was tremendously funny without losing his edge.
I'm a bit surprised that both Adams and Maher would steal this one without some attribution. I thought better of both.