Yeb, weather 'cross the pond will give the rider a "jump" on what is important, once the ride goes beyond a few hundred miles. Temperature and weather changes make it important to have good preparation and reliable equipment. Do not want to be out in the middle of nowhere with out a bit of light (strap on headlights keep hands free), some small handtools kit, for a bit of roadside work as well (spare fuses, tire plug kit, etc.), cellphone charger & GPS, canteen & snacks).
The bike is a given, there are plenty of bikes that will do the deed as Smitty says, but to make it a memorable one, you MAY want a good used bagger a couple years old, get the same enjoyment and not be out the cash while you work whatever skill set and touring style in to what you choose. Just don't make the long trip your equipment "shake down" cruise...you want to be riding awhile and get some good practice maneuvering your bike in some rather routine "tests" that occur with day to day riding. You want to be very well introduced to your machine and know how she handles when in knarly stuff as well as the super slab.