But the US doesn't have that resource everywhere, and the sheer volume of cars on the road that would need to be added to the network can't hope to match it. You can only use a renewable source where it works - thus solar isn't great in Alaska and water isn't great in the desert. Studies have been done - we have to go nuclear if we want to greatly lessen our fossil fuel use. Germany has done that in the past, as has much of Europe, b/c they don't have access to the fossil fuels themselves (see their Russian issues now) - they switched from relying on nuclear to relying on Russia b/c their renewables weren't close to enough to get through winters...