I'll take a stab at this, with the caveat that there isn't any one, right approach for packing for a cross country, or any bike trip, and I am sure you will obtain a number of opinions. After digesting all opinions/comments, you need to decide what makes you comfortable. Very few decisions can't be reverses. If you find you have over-packed, or you need something, you can mail the surplus home and you can buy what you need (in most cases) on the road.
I do not use a camelback because my jersey isn't able to breathe when it is sitting on my back so I ride hotter.
I use a NeoAir and I don't care how long it takes me to blow it up. I want to sleep as best I can if I want to be at my best the next day.
Sometimes I have taken a camera; sometimes not. But two to three pounds for a camera...I will not carry that weight. I have purchased a small camera that I also use for backpacking. It weights much, much less.
Like the camera, I have traveled with stuff sacks and without. At this time I like traveling without because what I found is with a stuff sack I am able to generate more room in my panniers, and then I am tempted to add something to carry because I have the room. Without the stuff sacks I pack more efficiently. I do use compression sacks for my tent and sleeping bag.
I do not like going without water. That happened once when I knew a roadside park would have water and then when I arrived there was a notice that it was not potable. So, I carry four water bottles of which I will always have three full of water and the fourth will be full depending on the planned water spots for that day or if I will be dry camping.
I have never taken a lock and I have never regreted that decision. I do take precautions depending on where I am when I stop. Usually those precautions include not stopping when it seems dicey and I try to keep the bike in sight.
I keep my electronics to a minimum because I do not want to carry the weight. I currently have a Galaxy tab (3G and GPS) and a cell phone, and they are off unless I need them so the power lasts a long time. I traveled once with equipment that would allow me to stay in touch and populate a blog. After that trip I decided never again would I carry that surplus weight and never again would I devote time to "entertain" others with my daily musings. It took time away from the purpose of the ride, which is, for me, solitude.
Again, this works for me and is apropo of nothing, so regardless of what you end up doing, enjoy your ride.