Small, fuel-efficient cars were around long before Toyota introduced the Prius. But an America drunk on cheap gasoline just didn't buy them, just as they didn't buy many Priuses (less than 1 percent of the U.S. market) until we were clobbered by rising fuel prices in 2007-2008.
Saying that does not demean the Prius's value. But it does put it in perspective. Truth is, if our political leaders had bothered to introduce an energy policy that forced consumers to pay attention to the true cost of gasoline, we would have had profitable sales of fuel-efficient cars and trucks long ago.
But that never happened.
Is the Prius important? Yes?. But did it start some kind of revolution in automotive fuel efficiency? Technical history says "no."
For that, I turn to the European Union, where governments sensibly demanded that consumers pay their share of the real cost of gasoline, forcing them to demand more efficient vehicles and to buy them at a profit to the manufacturer.
What is more efficient? Is it 50 percent of the market buying diesel-powered vehicles that are 30-35 percent more efficient than gasoline? Or, is it barely 1 percent of the market (in early years) buying Priuses?
As for hydrogen, et al, this country is making a serious mistake by putting that technology on the back burner while the Europeans and Chinese busily are working to put in place the infrastructure that makes that much cleaner and more efficient technology viable. As usual, we here have chosen to go with the sizzle in lieu of the steak, which is why, I suppose, we have more English majors than scientists.