The southern fox grape (vitis labrusca), is a bunch grape and hangs in somewhat large bunches usually about every third cane in large bunches, usually over 30.
Vitis Rotundifolia is always a muscadine or scuppernog and hangs either as a single fruit or maybe a few in a bunch. I've never seen more than 10 or so.
Both are native to US and can be found pretty much within all 48 continental states. The fox grape and muscadine are probably two of the best tasting native grapes to the US.