Maybe something on the Katy Trail in Missouri? Several companies offer self-guided or fully-supported tours. And I did my first two long tours, the GAP/C&O from Pittsburgh to DC and the P'tit Train du Nord in Quebec on a Cannondale Adventure 400 comfort/hybrid. A comfort bike might not be the flashiest or the fastest, but what makes a road bike fast and flashy can work against you on a tour.