With the huge number of Cirsium species, I don't see how one could eliminate all of the other possibilities at this stage. The leaves look like Cirsium arvense, and other species of Cirsium. Canada thistle is usually a patch, not scattered individuals, but I suppose the first few plants of an invasion could start that way.
http://oregonstate.edu/dept/nu...
USDA maps aren't always correct, but says SC is a bit below its' know range.
http://plants.usda.gov/core/pr...