The problem with this identification is the number of possibilities. Knowing the manufacturer leads us to several options. They absolutely did sell to the US, and many similar weapons can be found through some googling. One site AntiqueGuns.com, has what appears to be a matching weapon, listed as an heavy cavalry saber of Civil War era. The entry also has a lot of good background info on the company S&K, and a possible reference source to look at in the book CIVIL WAR CAVALRY & ARTILLERY SABERS by John J. Thillmann.
Unless you offer a reason why you think its American, I will also offer an alternative to this being a US civil war weapon. The model you have seems to be a very good match to one for sale at this site, Bygone Blades. This weapon is listed as an Italian 1860 Heavy Cavalry Sabre by Schnitzler & Kirschbaum. The images there show the exactly matching pommel, grip including the small rectangular cutout visible on the hand guard in you image, spear type point, and list the length at 89cm, matching your measurements exactly.
Whether or not this weapon was made for the American market or for the Italians, (or some others I haven't found yet) I think we can be confident in the 1860 Heavy Cavalry Sabre identification.
As to authenticity, I absolutely concur with the other answer. That should be left to a hands-on inspection by an appropriate expert.