OK, I'll make an assumption that this really will be an extended trip--at least a month and probably more; and that this trip will be in Spring or Summer. In this post I will simply sketch out one of many, many possibilities. From your starting place you will simply have to cross some of the western US states and some of the most impressive sights of the US. So I will give this as one possibility, just mentioning the major stops:
West Glacier (Hungry Horse for example and Mountain Meadows Campground) -- about 675 miles from your start, but you can plan intermediate overnight stops.
Yellowstone (West Yellowstone campgrounds abound) about 400 miles
Rocky Mountain National Park (Estes Park, many choices) 550 miles
Santa Fe, NM (for example Santa Fe Skies RV Park, a good choice) about 465 miles. In my opinion a must on this route.
Fredericksburg, TX and the surrounding Hill Country, especially if your trip is in the Springtime and the bluebonnets are in bloom--about 675 miles and you should probably plan an intermediate overnight. (maybe Carlsbad Caverns that would make it 400 miles to Fredericksburg.)
New Orleans at 580 miles. Maybe a stop in the Houston/Galveston area as an intermediate stop. I'm trying to keep this simple.
Now along the coast (yes, I'd stick with I-10 until past Pensacola) then to follow the west coast of Florida with a stop around Carabelle Beach --350 miles.
Staying on the west coast to Mykka River State Park 360 miles
And only 375 miles on to Key West.
Let's call this the Highlights of the Rocky Mountains and Dive South to the Coast Route.
To do any justice to these great areas of interest would be close to a month, but would make a great RV trip.
I'll leave you in Key West! But I have some great ideas for a return up the Atlantic coast and across the Midwest if you are interested.
Just a note: I've visited every one of these areas and routes I've mentioned in our fifth-wheel--but NOT on the same trip--many different trips.
