Way under-pack in the clothes department, a tee shirt takes up more space than you think. If you absolutely need something you'll soon be passing a store which carries one. Bring a tire patch kit and pump and chain lube. Oh, almost forgot, BABY WIPES and BABY POWDER!
I did a cross country run on my Versys this summer, 18 meandering days - California to South Carolina, 5,400 miles (2,100 in California alone).
California Hwy 101 and Hwy 1, are not to be missed.
I've also done a couple of 2,000+ mile runs up and down the East Coast this past fall to Rhode Island (thanks Twisted Throttle) and Philadelphia, PA and back.
Take half of what you originally pack (I mailed back two packages of "overpacking" as my trip progressed).
The more you carry means the more you have to deal with each night-less is easier all around.
Synthetic clothes pack smaller than cotton (and retain heat or breath better anyway depending on need) and wash and dry easier/faster.
Chain lube (my newly pre-trip replaced chain failed about 3,000 miles into the trip on I-10 in Texas; I was lubing each every other night - maybe should have done more-this was the only problem I had with the bike), baby wipes (or womens makeup facial wipes are even better for cleaning hands) and a small travel towel for cleaning the windscreen and visor of bugs.
Canister stove for camping to boil water/cook/make coffee, and collapsible silicon bowl for microwaving water in motels is also handy.
A wide mouth (can take ice) water-bottle or better thermos (for hot or cold) was my most used piece of non-rider/non-bike gear.
Here is what I took cross country:
I'm going to do another cross country trip (Seattle,WA to Charleston, SC) this Spring via a Northern route-can't wait!
Have a good trip!