” One of the 4 stars (think McChrystal) said the Marshall Plan was military counterinsurgency shrouded as economic aid. Truth?”
Yes, to an extent. After the numerous revolutions in 1918-1920, American thinking was that spreading money around in western and central Europe would minimize the chances of a repeat.
“What are the chances of an American coup by the 4 stars?”
I don’t know enough of the Inside Baseball on this to venture a strong opinion, but I’d guess it’s very slight.
“If/when the American Empire breaks up, would it be like Rome where the generals divvy up the country?”
I doubt it. Within the continental United States I suspect the state governments would come up with something: either go it alone or make a confederation with other states in the region.