Posters are asking where the money will come from. I doubt this is what congress and Obama have in mind, but here are some ideas.
Tax oil and cut subsidies to highways and airports. Fossil fuels have negative externalities and should not be supported by the state. Right now driving and flying are artificially cheap due to public funding of roads, street signs/lights, airports, security and traffic cops, etc. Not only should subsidies end, but a tax should be placed on carbon intensive travel to reflect the true social cost of driving and flying (loss of liberty/privacy due to the TSA and traffic cops, deaths from accidents, health costs from pollution, climate change, other environmental effects, etc).
The US government could also reduce it's dangerous empire. The USA has hundreds of military basses and spends more than the rest of the world combined on the military. It's time to put the interests of domestic social spending ahead of suppressing self-determination in the developing world. Military spending was a proxy for high tech development throughout the cold war. If we could invest in science and engineering to blow people up, we can certainly invest in science and engineering for green transportation and energy.
The USA also has the largest prison system in the world. Releasing those who committed minor crimes, especially consensual crimes related to drug use or sexuality would go a long way to reducing state costs. Better to spend $15,000 to put someone* on welfare or $20,000 to put them through community college than to spend $40,000 a year to incarcerate them.
*usually someone young and "of color".