jamis aurora. probably the cheapest "touring conscious" bike you can buy off the shelf. if you want to spend some more money upgrade the wheelset or look at the bianchi volpe.
my volpe made it across the county last summer with a jamis aurora following behind.
in all honesty, you can make it across on pretty much anything within reason (flame away). your current steed will do fine. ultimately, it comes down reliability and comfort. beyond that it starts to get compulsive.