I chanced on evidence that points to språng sashes in American Civil War uniforms, mostly in the collections of the Minnesota Historical Society. It's not conclusive, not without seeing the pieces, but in the pictures they look very like.
Most are red, with a few in buff for the rank of general and in green for medical officers. Most are silk; the wool sashes are for lower ranks and are in relatively poor condition, possibly from moth damage.
I feel rather pleased with myself, and fairly cross-eyed from sifting through online records.