There's a couple of other clematis that can be easily confused with SAC. If you were in my area, it would be Clematis vitalba, which is an imported vine that has become a noxious weed. It is less common on the east coast but has spread there in various area. More likely in your area is Clematis virginiana, which is a native that has naturalized throughout a good portion of the east coast and midwest.

Both of these are very similar to SAC in appearance - small white, fragrant flowers on rampantly growing vines and producing distinctive, very fluffy seedheads. Vitalba tends to bloom in summer and virginiana in late summer/early fall but exact bloom time can be variable depending on growing conditions.

The only way to ID SAC from these is by leaf shape and texture. SAC tends to have rather leathery foliage that tends not have any teeth or notches along the leaf margins - the other two have distinctly toothed foliage and less of a leathery, more of a normal clematis leaf texture. If you can post photos when the vine is in leaf, we should be able to help confirm ID.

FWIW, all are considered type III or hard prune clematis and can/should be pruned back severely in spring......but not many grow vitalba or virginiana by choice, unless it is a situation of a mislabled vine.