For what it is worth, I just went and had a look at an article on the European artifacts recovered from the Cherokee town Chota in Tennessee, and it reports that fifty-four clasp knives have been found, all but two of them of roughly the type under discussion (the other two being the French style), plus a bunch of fragments. In contrast, only eight sheath knives were found. These finds range from probably around 1735 up through the end of the 18th century, but the town had shrunk to only a few houses by 1783, so most of the finds are probably from before 1775, when it was burned by the American forces at the beginning of the Revolution.
I doubt the proportion of clasp knives versus sheath knives found represent the real proportions of these knives in use - I note that some of these came from burials, and items buried with their owners are likely chosen for symbolic reasons and may not directly represent what was actually owned and used by the deceased in life Plus, Cherokee burials from this site with grave goods skew heavily towards children under 13 with far fewer adolescent/adult graves having anything besides the body, for some reason.
Nevertheless, I think that the finds do indicate that folding knives were available and appreciated along the frontier. I've noticed that fixed blade trade knives of the butcher /scalper pattern don't seem to come much shorter than 6" and most are closer to 7" or 8," so I suspect that the folding knives satisfied the need for a smaller knife used for those myriad of tasks that don't involve slicing up dead animals or live people.
