Which way round are you planning to do the route? When I did it a few years ago I started from the east coast and went west roughly on your lower line, but we went directly south to begin with to take in the Outer Banks islands - Hatteras, Ocracoke etc. You might want to consider adding those to your agenda. If nothing else it'll take you away from the hell (imho) that is Washington and Philadelphia - unless you're specifically intending to visit them.

Your route from Salt Lake City to L.A. along the interstate is (again in my opinion) not a particularly interesting ride, but if you live in the area you probably know that anyway. It'll take you through Vegas though, which may or not appeal! (I'd had enough after a couple of days but it was worth the detour and there was certainly some interesting stuff to see (and lifestyles to observe)). We went north in and out of the mountains as far as Carson City and then east along route 50, stopping off at various places (and there were a lot of them) along the way.

Most of the time it wasn't so much the scenery (although there was some spectacular stuff to see, and not all of it parcelled up in national parks) as the people we met purely at random. There's more to be got from that side of a trip than purely looking at lakes, forests etc but it needs you to be open to it. If you're travelling on your own sometimes that can be a hard call. Just talking to people when you're hot and tired can be more than you want to do but I set out specifically to do that. I suppose it helped (mostly anyway) that I have a British accent and am old and grizzled so nobody sees me as a threat but I remember more of the people than the route.