The correct answer is France.
The XYZ affair took place during the presidency of John Adams. Adams sent multiple representatives of the US government to France to discuss the recent attacks on American merchant ships by the French. When meeting with the French representatives (who called themselves X, Y, and Z) the US representatives were shocked when they demanded a large sum of money to even discuss the possibility of a deal. This was seen as an extremely disprectful move by France and resulted in an undeclared quasi war between the US and France during the late 1700's.