I do not believe I claimed that American energy policy is irrelevant. Indeed, I believe it to be among the most important functions of the federal government and one of the major tools that will guide our civilization through one of the most challenging transitions in our history.
I also do not expect the clean energy challenge to be particularly similar in operation to the Manhattan Project. I used Manhattan as an example to illustrate that engineering challenges with a grand national mission are possible without grassroots support, conducted by elites. The creation of the Internet is the better example, which was an example of a Defense technology that achieved commercial application and eventually induced broad popular demand, where there was little to none before.
I would be more optimistic about grassroots activity if it had not failed in several metrics thusfar. A successful grassroots campaign would be growing in popularity, not shrinking, but polling shows fewer Americans care about global warming than did in recent years. A successful grassroots campaign would see their demonstrations garner significant national attention, but 350.org's Day of Action--the "biggest day of action the world has ever seen"--was largely ignored and forgotten, and appears not to have affected legislative politics in the slightest. A successful grassroots campaign to avert catastrophic climate change would embrace effective policies in their advocacy--increasing public spending on R&D, driving deployment and innovation, supporting nuclear power--but grassroots activists are not doing this.
But these are not failures of tactics so much as framing. There cannot be a successful grassroots campaign to avert climate change because the cause of climate change is predominantly technological, not social or political. The process of driving technological innovation is something that even my precious elite do not have a firm grasp on, let alone the droves of climate activists calling for an end to global warming (and stopping there). And while there is a role for social and political action--especially in early adoption and effective issue advocacy--the main goal of making clean energy technology cheap will be accomplished by elites.