People tend to give American Presidents far too much credit or blame for the US economy. They simply do not have the power to change it or even shift it very much or very quickly. They are much more at the mercy of the economy than it is at theirs. A dictator like Idi Amin had almost direct access to the economic engine of Uganda. He forcibly took many businesses from their legit owners and handed them to party cronies, who mismanaged them. The damage to the economy was a direct result of his policies and actions.
God authored the metaphor not me. What you are saying is true but America's Idi Amin is a customization. Idi Amin did all he could do in his setting, and Obama is doing all he can do in America's setting. You don't have to have a line by line parity for the metaphor to work. What Idi did for Uganda Barry is doing for America.