RIB47, when I hear "all -terrain" I'm thinking there's some hills and steep sections involved in which case carrying the least amount of gear and having it well secured would be as important as the bike design. Otherwise crappy roads can be dealt with using fatter tires. Your criteria for "dedicated touring, casual road trip day bike AND PanAmerican Hwy type terrain" covers one hell of a range, at least you're not asking for fast single track riding over logs and ruts which points to a mtn. bike with shocks. If you're thinking of road trip day bike AND loaded rough terrain tourer you're asking for a lot. If you're light you can pull it off better than if you're heavy.

Cross Check or similar bike that can take fat tires would fit the bill. You might consider having two sets of wheels. Light road wheels/tires and heavy touring wheels/tires. Keeping the load light with fat tires taking up the shock can get you through a lot of rough stuff but at some point shocks become worthwhile. For $1200 you've got some compromising to do. LHT with 26" wheels and two sets of tires would be another thought if your dedicated touring involves some weight.