IIRC it was first documented in America but probably evolved in Africa. Though no one knows for sure, it's speculated to originate in the 19th century.
If something like it evolved earlier it would compete with variola major and a lot of people would have survived, changing history everywhere. Smallpox killed thousands in Europe every year. If it evolved in isolation in the Americas or Americas and SS Africa then it would greatly reduce death from variola major introduced by the Spanish. Though there were a multitude of diseases in the Atlantic Exchange, many just as deadly.
Variola minor killed less than 1% of those infected. In virgin soil situation it might be worse, but fatality would probably still be low as the morbidity of the disease is low to begin with (the infected didn't get terribly sick). The vast majority of natives would still die from other diseases, but it would slow Spanish conquests. Some areas may not be conquered, and the native population would be more numerous today, with some extinct tribes still in existence.