Working backwards, the percentage of green and tech jobs now, compared to manufacturing and other jobs lost is not a static number. If this crash has shown anything, it is that the system changes when it breaks. The green economy, if it really does come alive, has barely twitched so far. It's also too general a term to answer with "as soon as..." There is a struggle going on now. Subsidies and credits for US manufacturers of, say, windmill parts, could put Detroit in ther running for the leading position in the manufacturing such things. While we wrestle with whether or not a second round of stimulus will ever be needed, developing economies are offering companies amazing deals to set up shop in their countries. The green jobs are coming. The question is whether or not they are coming here.
We can produce things, and we need to produce things. We're still a nation full of inspired people with great ideas. We can invent, fix and thrive... unless people get in the way on purpose. Otherwise, we might actually only be beginning to sink.