I don't really have experience with either but I know grey and American golden are difficult to tell apart. This bird looks like a grey plover to me with its heavy-looking bill and relatively shorter wing feathers, but the supercilium looks more like that of an American golden. On balance I would say grey plover.
Aw, the confusion of common names!! Based on the bill, it does look like a juvenile Black-bellied (aka Grey) Plover. It is hard to pin-point an exact id via a photo of such similar species.
