Is this a loaded tour (i.e., you're carrying your own gear on your bike) or a supported tour (there's a truck carrying your gear?) Organized tour with the route all planned out, or are you going to be on your own?

How many weeks are you going to take to cross the country? i.e., what sort of daily mileage are you going to do? The first issue (since you're apparently rather new to riding) is that you need to get your position on the bike dialed in. You're going to be on that bike for hours each day for weeks on end.

I know of several cross-country organized tours that keep the daily mileage in the 60, 70 miles a day range. By itself, that isn't too much. You will "ride yourself into shape" after the first week or two, so you don't need to start out feeling like Superman, but I would be riding every chance I get. Do at least one long ride a week,