Likewise, large sections of the Blue Ridge Parkway, especially in North Carolina are closed in the winter due to weather.

Having just done both coasts in the last week, I can echo everyone else's sentiment that it's too much. Definitely pick a region and go with it. Also if in the Bay Area, a day or two trip down to Monterey and Carmel area is also worth it. I highly recommend the Tickle Pink Inn. Funny name, great place to stay.