Since your request is so out of the ordinary, please provide as much specific info about yourself as possible, i.e. is this hotel only, camping only, cooking/eating out, miles per day you ride, any time constraints (must be done by X date), what kind of gear & bike you have, etc.
However, without that info, I will say that most routes (with detours due to winter closed passes) are possible if you are willing to get hotels when needed (12" of snow on an ordinary tent will collapse the tent and break the poles most likely), sometimes staying at same hotel for days at time as you wait for the roads/pass to clear. You would also need to have the appropriate riding clothes for cold, wet weather, and if camping, have true 4-season camping gear based on the coldest areas you expect to encounter. Expect to go slow overall due to increased time off the bike waiting out storms, etc. Obviously, you will be cold. A lot of services will be closed, especially out west.
Suggest you check out WeatherSpark.com for weather averages anywhere in the world. Remember, to look carefully at the temperature bands (normal, extreme, etc.) and precipitation info. Riding in 35*F wet weather would not be fun to me. Doable, yes. Enjoyable, no. Why ride if you are not enjoying it if you do not have to.
Honestly, I would suggest you go to S. America (or at least Mexico). They have some beautiful routes there and other than the cost getting to/from S. America, it is relatively inexpensive. Another option is to head slowly north from Key West towards Bar Harbor, ME, then into Canada to the NE if you want to "cross the country". The final option I would suggest is to go from Key West counter-clockwise along the Gulf Coast to Brownsville, TX. Definitely more traffic between Panama City, FL, to around Corpus Christi, TX, (rest can have fairly quiet back roads) but also a lot warmer and more services.
Best, John