So, I was thinking about TLs where the Old Worlders never reach the Americas for a variety of reasons, and obviously the main problem with New World advancement is lack of megafauna.
I did some research, and apparently the wild ancestors of llamas were FAAAAAAAR smaller than actual domesticated llamas, and I wondered, how long would it be before humans could breed llamas that were large enough to use as a horse? Already they were used as pack animals, and a larger llamas means more cargo and riders.