Were sabres used effectively in U.S. Civil War?

[Dmitry]

I think you've answered your own question.
Less then 1/10 of 1% of injuries, let along casualties in CW were inflicted by a sword or a bayonet. Artillery did the job on the rest.

Cavalry saber was not a totally useless implement after all, for many a running Indian were cut down in the following decades, more so for the sport of it.