Did the American's assist with / perform this supply mission? Para-dropping cargo into the sea in floating containers/pallets doesn't sound like a routine mission for RAF C130s, but I could be wrong...
Lots of things come out of the back of an RAF C130... why would it be something the USAAF do but not the RAF?
Anybody looking for covert flight ops by US forces is barking up the wrong tree. Corporate, initially, provided a huge challenge - the distances between Ascension, Falklands, and S Georgia were huge, we simply couldn't fly from A to B...look at the Black Buck missions (read Vulcan 607) - tankers had to refuel tankers so they could go far enough to refuel the bomber. The US provided intel, they may or may not have provided a few nutters whose lifetime subscriptions to 'Soldier of Fortune' ran longer than they did. Nobody flew off Wideawake from area 51. There are very few secrets to be discovered <g>