there's an annual event in Iowa that's become quite large.... The
RAGBRAI, that is the Register's Annual Bike Ride across Iowa... I know of a few people who've done it more than once (I also think our own Beetle Bailey has has done it) It might be too late, but see if you can get yourself into the lottery for that - it's a lot of riding... but from what I understand the event itself is worth it...
Riding across the country -- you do realize this is a big country... with lots of hills and mountains... Doing it alone sounds dangerous... 6000 pounds also sounds like a lot of money to do it as part of a group but sounds safer... Why not rent a car, a convertible, and drive it...