1. Build a compact fuel cell car motor that can fit most cars. Make it generic and build adapters to increase the number of cars that it will fit. It doesn't have to be perfectly efficient. Most people will settle for the inconvenience of filling more often if they don't have to pay ridiculous prices at the pump. Keep the cost of switching low with government subsidies, say $500. Cost ~$500 million. Timescale: 6 months to engineer. 18 months to distribute, including techincian training.
2. Introduce quick charge depots at 50,000 gas stations (about half). Cost ~$200 million. Timescale 6 months to engineer. 6 months to distribute.
3. Educate the public with TV commercials, flyers, etc. and explain that gas tax will increase to punitive rates - $20+ gal 1 year from now. Cost for public awareness campaign offset by revenue generated by the 20% who would rather pay than switch.
4. Offer rebates, vouchers, etc., for those in hardship situations so they can switch. Cost $100 million. Timescale 18 months.
5. Increase in use of Solar, Wind, Wave, and Current power dramatically, by offering tax incentives to clean energy companies, and corresponding tax hikes for carbon/fossil energy companies. Cost negligible. Timescale 1-2 years.
Total cost less than $1bn. Easy. I'll do the math later and correct the figures. I wanted to get this posted asap. And, no, I don't expect anyone to say, "oh what a good idea" and rush out to implement this plan. It will takes research, homework, and a will to succeeed. But it will generate jobs, it will stimulate the economy, and it will do more for America's image in the world than anything else in history. And it will disempower the anti-American oil states.
If I had the $, I'd build such an engine right now. Sure, there are technical problems to solve, but they are solvable. Nothing here is new technology, just new ways of using it.