Four years ago we went from Los Angeles to the Maritimes down to Florida and across to DFW to Q and home. Gone 10 weeks saw 37 states, 7 Provinces and innumerable NP sites. Great trip. We went to see what interests you. Make a list, get some maps buy some stick on arrows, put them pointing at your POI's and plan a route. You didn't list a time frame either so it's hard to give much information.
We were glad to be home but we are planning on retracing some of the steps.
Now if you want to know what we liked best