According to my mechanic friend, several auto makers made vehicles that went 200-250 miles on a gallon of tapwater, and they would have gone into p;roductiion in America, if the US Government allowed it.
Hydrogen fuel cell technology has been around for about as long as we've been using internal combustion engines.
Probably the biggest reason we're not all driving hydrogen fuel cell powered vehicles now is because it would be nearly impossible to erect any sort of monolithic industry around the concept: anyone with the space and a little know-how could put together their own refinery in their garage.
It would be almost impossible for a corporation or cartel of corporations to create an infrastructure whereby the public would be dependent solely on them for thier fuel supply.
On the other hand, the petroleum industry was already one of the dominant industries in the world by the time the internal combustion engine came into use.
So, while billions of dollars have gone into the development of applications for internal compustion technology over the last 100+ years, very little has gone into the development of hydrogen technology, and if anything quite a bit of money and pressure has probably gone into its suppression (there's a popular conspiracy theory that the Hindenburg disaster was orchestrated by the oil industry tycoons in order to make the public leary of anything hydrogen related).
The truth is, hydrogen fuel cell technology makes sense. It's easy to make, an adoption of the technology would involve a conversion of several aspects of existing automotive production rather than a total abandonment, and the production and use of hydrogen fuel cells results in almost no negative impacts on the environment: hydrogen fuel cell engines themselves are zero emission.
Tesla is working on a hydrogen fuel cell car that they're they're planning to put on the market in 2026.