Jeffery's correct. If you look at a topo, you'll notice that some of your craters are actually hills. Most of the Florida ones are identified sinkholes and/or springs. A few that I looked at were simple farms built in the inside bend of a river or large creek, making the border rounded.

However, a great many of the ones in the Carolinas are the "Carolina Bays", the origin of which are disputed, so you're as right as anyone on those....they could all be impacts.