Yes, there are native Clematis in the USA. There are also cultivated ones that have been spread by birds etc. into wild areas.

Is it this one?

http://www.ct-botanical-society.org/galleries/clematisvirg.html

If it is white, blooms in late summer/early fall, and has a fragrance it sounds like sweet autumn clematis. Clematis virginiana blooms have no fragrance. The leaves on SAC are similar to those of a lot of other clematis. The leaves on C. virginiana look more like the leaves on the macropetalas.

Sounds like the sweet autumn one. Now how do I tame this thing. It comes up everywhere, yard, trees and other flower beds?

SAC is a very aggressive plant and seeds itself quite rampantly. What I have found helps tremendously is to cut the old flowerheads off as the flowers begin to fade. Other than that using roundup to kill them completely is the only alternative that I know of.

I don't know if anyone else has this problem, but I am terribly allergic to SAC. It is beautiful, but a killer for fall allergies.

I am constantly trying to eradicate it, but it can get away from you in no time. The only thing I know as invasive as that is trumpet vine. Also impossible to eradicate. You can cut off your own seed heads, but your neighbors more than likely have them too.