The Prius and others are interesting experiments but it will only be a small percentage of cars sold for many years to come. We also have to look at what we can do with the rest of the fleet. 54.5 miles per gallon by 2025 is an an extremely modest, if not pathetic, goal. My eight year old Citroën C5, considered a big car by European standards, is around 40 mpg. If I were to update to say a brand new Volvo V70 - also a big, comfortable and safe car - I'd do over 52 mpg (and less than 119 g/km CO2 emissions). Even a couple of years old V70 would do over 48 mpg! And we're still talking 'big' cars while the 54.4 miles per gallon by 2025 is for the average car fleet sold. Two or three years and modern cars will bloody BE at 54.4 mpg - and you will still wait for another ten years?! You might as well shut your motor industry down right now.
No, the faster American motor industry gets up to modern standards the faster it gets more competitive! The Ford F-series, a dinosaur relic to be honest, is still the best selling car in the world - THAT IS F**NG AMAZING - but its more or less unsellable anywhere but in the U.S. for being so old-fashioned and having a mileage that wasn't ok even in the 70's. What will you do when if finally stops selling? The U.S. have a grand automotive heritage to defend and you are losing it. This goal is too little and too late. Where did the American confidence go? Why don't you set a goal to ASTONISH the world rather than one that makes you look pathetic.
It makes me sad, I know you can do so much better than this. Fire your lawyers and get your engineers to work, you can do it if you want to!