A lot will depend on how heavy or light you will pack, but if you are fairly light weight and pack light the wheels may be okay. You will want some lowish gears, not necessarily as low as some here will tell you, but you will be crossing mountain ranges if you ride across the country.

Choice of baggage can vary widely depending on how much you carry. If you will be carrying 40-50 pounds of stuff you will likely want 4 panniers. For 10-20 pounds of gear you can get by with some pretty minimmal baggage. And yes you can travel for months on that light of a gear load.

I suggest thinking about how what/how much you will carry first. Then decide how you will pack it and on what bike.