On my cross USA trip I used a combo of AAA state maps and free maps from tourist information centers.
On one trip I tried to use DeLorme maps on a netbook but it was incredibly annoying - as soon as you zoom out far enough to get a big picture to plan a route, the roads disappear. And it takes power, and it takes time to dig it out of the bag and start it up. I like paper maps a lot better.
I would think by the time you finish printing a set of cross country maps, you'll be carrying a ream of paper and will have spent enough money on printer ink that you could just get an AAA membership.