I'd highly recommend not to travel via the interstates. The secondary roads are just fine for RVs and you'll see a lot more countryside. We did it all the time with our 40' motorhome.
I think you've got to help us a little more on what states you hope to see. You've made a BIG request.
You're starting in British Columbia but said you don't want to do the western states. For starters you could get on Hwy 2 through Montana and take it into Michigan for awesome scenery along the Great Lakes.
From Michigan you'd have many choices to get down to the Florida Keys depending on your interests - historic areas, beaches, forests w/lakes and rivers....
When ready to head home from Florida travel through the lower southern states of Alabama, Mississippi, Louisiana, Texas then into New Mexico and head northward.
We always enjoy state parks and in the southeast you'll find many Corp of Engineer parks that have very nice sites on water.
