It may or may not be the most "efficient".. I attempted to find unbiased report.... for or against...yet to find.
Direct numbers of the ecconomics aside....
Without the military and the secondary, tertiary, quaternary spending et al.. the U.S. would collapse for a number of years...(I predict a more than a decade) before recovering to a new ecconomy. It would not change the disparity between individuals-- it would resemble the crash of the great depression. The hearty bourgeoisie would still thrive and the proletariat
Class would increase.
The insular nature of Americans as a whole, would overwhelm those technocrats who would otherwise be the driving force of the "renaissance".
Would the U.S. / World be better without the countinued escalationism of Domestic and Foreign Militaries? Probably...
You forget the one variable that will always prevent... the near immutable "human Condition"
We may esotericaly strive for betterment... but our base nature.... aspiration, conflict, competition....mortality will always prevent us from the transcendent utopia that socialists espouse.