I drove 8000 miles from Chicago to LA and back, westbound to the north through S. Dakota and Montana, down to Yellowstone and over to California, then back thru Utah and Colorado.
What you bring depends on what you plan to do and how you plan to stay along the way. If you are going off-road or camping, you need some basic equipment. if it's just highway driving , that's simpler
I think the most welcome piece of equipment on my trip was the Satellite radio.