In '06 I rode a Trek Navigator 200 from Nova Scotia to Ciudad Victoria, Tamaulipas, and then, after 10 weeks in Mexico, up the Rio Grande from Brownsville to Alpine, TX. I chose that bike for the comfort of suspension and an upright position. I geared it as low as possible, and used SPD pedals and shoes. I wore out two chains and two sets of brake pads and had one flat tire (Schwalbe marathons - don't leave home without 'em), and absolutely no other problems with the bike.
I put on front panniers and a handlebar bag, tied a milk crate to the rear rack and towed a BOB trailer. All told I had 70 lbs of gear. About 20 pounds more than I should have had, but I managed it alright. I could have managed with a smaller tent and without a laptop, but my tent was comfortable and dry and email and Google Earth were worth the extra weight.
Loneliness and fear were the greatest obstacles. I lost twenty pounds and got very strong. I met some very fine people. And my rear end got so sore that I would be in agony at the end of the day.
I'm 68. I'd love to do it again. Maybe with a recumbent. Any 'bent tourers around here?
George