We took our less than 2 year old son on a road trip to Colorado. This was a 3,000 mile round trip for us. The only problem I can recall was that he locked DW and me out of the motel room on one occasion. A couple of years later we took our son who was about 4 years old and our daughter who was less than a year old on a road trip to Gatlinburg, which is about a 1,500 mile round trip for us. No major problems that I can recall. We simply did not go anywhere that was not appropriate for small children.
Bear in mind DW was a stay at home mom who had no use for daycare or babysitters (even grand mothers or aunts). DW breast fed both of our children until they were weaned. They never used a baby bottle. Wherever we went, the kids went. So, a road trip was no different.
Honestly, IMHO, it is much easier to travel with infants than with teenagers.