Many ways in which Benjamin Franklin is claimed to have set the tone for America is a reflection of the fact that America was already America and preset when Franlkin was coming of age. America was also setting the tone for him, a curious young man growing up in a society that was open to being free.
Franklin and his peers were the counterparts of today's tech entrepreneurs. Instead of shaping designing apps and ecosystems, Franklin's peers were designing societies and the Republic.
Isaacson observes that, among other things, Franklin was the father of this American trait that is self-deprecating humour. It is hard to tell what the counterfactual would have been. The bar seems low; Americans are not particularly known for self deprecation even post-Franklin. Franklin's far greater contribution to the American character is best captured by Edmund Burke's adage “Magnanimity in politics is not seldom the truest wisdom; and a great empire and little minds go ill together.”
It may be hard to re-assess the wisdom of the forefathers, for their wisdom has been stress-tested in the environment that is quite different from ours. The fact that the environment was different from ours does not mean it can never come to pass again. So, we should not discard the institutions of the ancients on a whim.