Actually, I don't believe that is quite true. As stated, the process would require 100 percent efficiency, and I don't believe that to be obtainable.
However, I do think it would be possible to create large scale sun-to-electricity or wind-to-electricity facilities in non-populated areas and pipe or ditch water to them. The water could then be converted to hydrogen and oxygen by electrolysis without the loss of too much power through long distance voltage drops. The two elements could then be shipped to wherever they are needed.
Fuel cells, internal combustion - and other types of engines might be feasible.
Now, if we could just get a source of electricity to destinations without too much voltage drop due to the distance, it might just be feasible to create a car that never needs re-fueling. Just fill up a permanently sealed, heavy gauge fuel system with water; conver the water to hydrogen and oxygen during the night; convert the hydrogen and oxygen back to water as the car is used, and recycle that water again at night. The only thing needed to be added is the electricity at night. Wouldn't that be a "gas"!
EBUCK