So, what nations produced the most successful privateers?
I'd like to see what people think and I would like to see some reasoned arguments (which all of us do anyway )
Obviously Sir Francis Drake was very successful as a privateer for Queen Elizabeth (though he's a bit early of our era), but Spain considered him a pirate because his actions took place in a time of peace.

Charity

My vote would certainly be for the American Colonials. The damage they were able to inflict in seven years of exhuberant commerce raiding not only deprived the English army of a number of vital supplies, but took a savage toll on English shipping insurance rates.

Best,
Charles

Not exactly the case you mention but pretty close. In 1779, Abraham Whipple in command of the Providence with the Ranger, commanded by Thomas Simpson, and the Queen of France by John Peck Rathbun were cruising off the Newfoundland Banks where they found themselves in dense fog in the middle of the 60 ship "Jamaica fleet". The fleet was guarded by a 74 and several frigates. They captured eleven ships without firing a shot. The cargoes sold for over a $1,000,000.

Abraham Whipple had been the captain of the privateer Gamecock which captured 23 French ships in one six month cruise in the previous war.

Technically, the Providence, Ranger and Queen of France were naval vessels and not a privateers, though the distinctions seem to become blurred. Where is is often said that the line between privateering and piracy is thin (a view I do not necessarily share), in this case the line between the navy and privateering became very thin indeed. A song of the period celebrating their successful cruise, calling them privateers.

"Come listen and I’ll tell you how first I went to sea,
To fight against the British and win our liberty.
We shipped with Captain Whipple who never knew a fear,
The Captain of the Providence, the Yankee privateer.

Chorus: We sailed and we sailed and kept good cheer. For
not a British Frigate could o’er come the privateer."


The Whipple Family blog

These three ships were substantial vessels (two frigates and a ship sloop) of the American Navy. After capture, the PROVIDENCE became PROVIDENCE 32 and RANGER became HALIFAX 14 in the RN. The QUEEN OF FRANCE, which seems to have carried 28 guns, was destroyed at Charleston.

The number of prizes taken in this instance seems to vary with the source.

They were indeed substantial ships, by American standards, if not necessarily by the British. The QUEEN OF FRANCE was an old merchant ship purchased by Franklin and Deane in 1777 a refit as a 28 gun frigate. The PROVIDENCE was 28 gun frigate built by Silvester Bowes at Providence, R.I., launched in 1776. The RANGER, of course, was an 18-gun ship sloop, launched in 1777 commanded by John Paul Jones before he moved to the BONHOMME RICHARD.

The number of ships captured seems to vary in reports between eight and eleven. Apparently eleven ships were captured but three were subsequently recaptured. The eight that made it back to port were reported to be the richest prizes of the war.

Cutting out eleven ships without firing a shot from a fleet of 60 ships guarded by a 74 and several frigates is quite impressive.