The abatement of American ambitions is something the world has long, not to say desperately, awaited.
Not that Americans should not aspire; indeed, the world has long loved us best when we dream most generously the utopias of which we forever will dream as long as we call ourselves Americans. It's only that generosity, not the reverie, of which we've lately lost the habit.
I see things slightly differently.
Big failures whose practical and theoretical lessons and new wisdoms are then put to use, more carefully, ambitions unabated, teach things, and take technology to unexpected places.
But big failures, institutionalized as big failures, become devastating craters of resources, warding off further attempts for years or decades … but only after the fact. That didn’t need to be their legacy.