Great question! The Cullasaja River is in western North Carolina, where many Cherokee lived when English (mostly) settlers arrived. Cullasaja is an Anglicization of a Cherokee word so it wouldn't have a Spanish pronunciation. I figured it was /Cull uh SAH jah/ or /Cull uh SAY jah/ where "Cull" rhymes with "dull" or maybe "pool". I didn't meet any Cherokee (that I knew of) to discuss it with. Wikipedia says that it's "Cull" with a short u (so it rhymes with dull) and the second a is a long a. So /Cull uh SAY jah/. I was very close.