Final answer:
Marquis de Lafayette from France was the 'secret weapon' that helped the U.S. win the Revolution.
Step-by-step explanation:
The 'secret weapon' that helped the U.S. win the Revolution was Marquis de Lafayette and he was from France. Lafayette was a French aristocrat who volunteered to join the American forces during the Revolutionary War and played a key role in the American victory.
Learn more about Marquis de Lafayette's role in the American Revolution