Some numbers for the green power electric transportation dreamers:
14 million barrels of petroleum per day of transportation petroleum. Each barrel has 5.8 million BTUs of energy. Multiplying, that is 81.2 million million BTUs. Internal combustion engines are about 25% efficient, so the USA requires energy of "only" 20.3 million million BTUs per day. Since electric motors as used in electric cars are about 90% efficient, that means we require 22.5 million million BTUs per day. But battery charging is also about 90% efficient, so we then need 25 million million BTUs per day. Then, unless we're charging the batteries right at the power plant, we have to figure in the 93% efficiency of the power grid, so we really need 26.9 million million BTUs per day. There are 3413 BTUs per KwH as a conversion factor, so we need 7.88 billion KwH per day. Since there are 24 hours in a day, we need a generating capacity of 328,000 megawatts. The Palo Verde nuclear plant in Arizona can generate at a rate of 3810 megawatts. Dividing, we find that we need about 86 new nuclear power generating plants the size of our largest one to power US transportation completely and completely green.
Wind? Biggest wind machine so far is 8 megawatts, so we'd need 41,000 of them, but probably, for a fudge factor for the times that the wind doesn't blow sufficiently for 8 megawatts, we'd probably want maybe 4 times that many, or 164,000 really big wind turbines. There are 3,794,083 square miles in all of the USA so there would be a density of 0.043 wind turbines per square mile, but of course not all areas have wind or can be built (mountains), so maybe we'd get to needing 1 square mile per turbine. Doable, but how much would it cost? Read on internet 1.6 - 2.2 million per megawatt, so the large 8 megawatt turbine would be $17.6 million on the high end, and 164,000 of them would be $2.88 trillion. Build 'em out over 50 years or so and yeah, that's "only" 57.7 billion dollars per year. Chicken feed for a gov't that is already broke, eh? In contrast, the Palo Verde Nuke plant cost $5.9 billion, so 86 of 'em would cost $507.4 billion - lots less than $2.88 trillion for wind.
Solar only produces during the daytime. Not going to try to calc that.