I've never used CB, but the 2m calling frequency is pretty active coast-to-coast. I've driven coast-to-coast on I10, I40, I80, I90...and never was out of reach of other hams on .52 on 2m. Ever. There are a few places where cell phones don't even work, at least last time I checked...which was 3 years ago, so it might be better now. I 40 doesn't quite go coast to coast, but pretty close. It ends about 100 miles inland from the Pacific. The others make it all the way. Be prepared in some places for 'miles and miles of nothing but miles and miles' until you're east of the Mississippi river, and then towns are closer together. My ex-GF from years ago contacted me to tell me about her adventure driving from L.A. to Lubbock, TX on I40. Her car broke down in Kingman, AZ...and the rest is a long story. But when you're in the middle of nowhere, be prepared.