Join Date: Jan 2016
Location: Livin' in a Poor Man's Shangri, La. aka New Orleans
Maybe it sounds a bit pedantic, but rather than carrying "stuff" (that you'll likely not need) I would recommend having the bike's servicing completely up to date and not thinking you'll do it on the way. Even better is if you do it yourself to know the bike. You will then be able to see things that might mean a trip to the dealer before you leave, or a post here for advice.
The services, esp the 6k one, is easy. The 12k one is a bit more complex with changing the air filter and checking valve clearances, but very worthwhile to do...and don't be afraid of doing the service early. Make sure the bike is up to date on brake fluid flush, a 16 would likely have 2 by this time, initial and after 2 years.
Re tires...for me trickier, because I like to get maximum safe mileage out of them and that means close to the wear bars...I have changed them, at a dealer, along the way. If you prepare ahead for that it's cheaper, but logistically harder, usually takes half a day from your ride. Some dealers will fit you in immediately, others will not ( I have had good luck with Eurosports in Salem Va and Iowa City BMW, those places may be on your way, Sandia BMW motorcycles in ABQ and Santa fe are top notch also, and I like the peeps at the Transportation Revolution here in New Orleans).
So, I am facing a rear that has 1000+ miles left on it (I think) and a front in decent shape, do I change before I leave or along the way...the jury is out on that right now.
I don't take "spares" of anything, but do take the aforementioned things like the zip ties--including some stainless steel ones--duct tape, rubbing alcohol, instructions for my Sena, tire plugging, CO2 carts and a pump. I have the owners manual as a pdf on my phone.
WATER is probably your most important "spare" if you are crossing the US in the summer