Excellent point, joule.  Alternative energy is a (highly under-rated) form of civil defense.
They understood that in WWII, they were called 'victory gardens' for a reason, walking and riding bicycles was extolled as patriotic, and substitutes for things were used to great acclaim - WWII is where margerine came into its own (yuk!).

There was not so much of an alternate fuel push because the US was the world's swing producer of oil and most of the carpooling and gas rationing was to save on TIRES rather than gas, so using hemp for fuel etc would have had people driving more and using up their tires.