The U.S. middle class's path of success ended precisely when the gold standard currency system was replaced by the floating-currency system in 1971. Prosperity is built on the foundation of a stable currency.
John Galt's "rational self-interest" is a fantasy. Tea Partiers and Libertarians need to reconcile with this fact, but it will require far more thought than they have customarily been willing to spare.
What is left out of the description of his theory in regards to counter-cyclical fiscal policy, is that Keynes also believed that in times of relative prosperity sovereigns should create budget surpluses.