Have done many US road trips over the years when working away. A lot of what you want to see/do and the enjoyment you get from it will come down to the time of the year you decide to pack up and go. I always found September/October time perfect for both the North and South route and helps that the schools and college's have just returned after the summer break.
So many little things you never think about will crop up, I know you say you dont mind driving long hours (good job when taking on parts of Texas) but depending on the part of the day you choose to do the majority of your driving if you are driving into the American sun that is beating down hour after hour straight into your face it can get you down pretty damn quick.
Will be great fun in an RV and means you can really make the most of any National parks you choose to visit. (again dependent on the time of year you go) When you hit up the big cities some of the best fun can be had by driving just a few miles in either direction until you stumble on some great little towns where you get much cheaper prices and get a feel for the real America (if thats what you want) also speaking to the locals they will point you in the direction of some real gem little places that will never have even thought of.
New England in the fall and a ranch stay in Montana were a must for me but without a doubt the most stunning drives were along the West Coast from San Diego up to Seattle taking in the like's of Santa Monica, Laguna beach, Big Sur, San Fran etc.
Finally try not to be to strict with itinerary and allow for big changes, something on your bucket list that you will have wanted to do for a lifetime may end up a big disappointment, yet something that you stumble across by sheer accident will end up being something that you will never forget.