Topaz

In 1962 Copenhagen, a high-ranking Soviet intelligence officer, Boris Kusenov (Per-Axel Arosenius), defects to the West. During de-briefing, CIA agent Mike Nordstrom (John Forsythe) learns that Russian missiles with nuclear warheads are to be placed in Cuba.
Needing physical evidence, Nordstrom discloses Kusenov's name to French agent AndrÃ© Devereaux (Frederick Stafford), asking him to bribe Luis Uribe, a member of Cuba's U.N. delegation, to provide photographs of documents confirming the missile bases in Cuba. Devereaux decides to accompany his daughter MichÃ¨le (Claude Jade) on her honeymoon to NYC with son-in-law FranÃ§ois Picard (Michel Subor).
In New York City, a French-Haitian agent, Philippe Dubois (Roscoe Lee Browne), is to contact Uribe, who is the secretary to Cuban official Rico Parra (John Vernon), who is staying at the Hotel Theresa in Harlem to show solidarity with the African American community.
Dubois sneaks into the hotel. He bribes Uribe to take the documents from Parra's office to photograph. Parra catches Dubois photographing the documents. Chased and shot at by Cuban revolutionaries, Dubois purposefully knocks into Devereauxâwho was watching events from the other side of the streetâand slips him the camera. A red-headed Cuban guard helps Devereaux to get up, but lets him go. Dubois escapes into the crowd around the hotel.
Dubois' photos confirm that the Soviets are placing missiles in Cuba. Devereaux, despite his wife's accusations of infidelity, flies to Cuba. His mistress, Juanita de Cordoba (Karin Dor), was the widow of a "hero of the Revolution". This enables her to work undercover in the resistance. Upon his arrival, Devereaux finds Parra (another lover of hers) leaving Juanita's mansion. Devereaux asks Juanita to take photos of the missiles. Juanita's loyal domestic staff, Carlotta and Pablo Mendoza, pose as picnickers and photograph the missiles. Pursued, the two hide the incriminating film before they are captured.
During a mass rally and lengthy speech by the "lÃ­der mÃ¡ximo", the red-headed Cuban guard recognizes Devereaux's face from the New York incident.
Parra, has heard from the tortured Carlotta Mendoza that Juanita is their leader. He embraces her, shooting her dead to save her from extreme torture.
At the Havana airport, the Cuban authorities fail to find the microfilms on Deveraux. When Devereaux gets back, his wife has left him. Devereaux is to be recalled to Paris. Kusenov tells him about the existence of a Soviet spy organization called "Topaz" within the French intelligence service. He is given the name of NATO official Henri JarrÃ© (Philippe Noiret), who leaked documents to the KGB.
Devereaux researches the leak. He invites some of his old friends and colleagues, including JarrÃ©, to a lunch at a fine Paris restaurant under the pretext of helping Devereaux prepare for his inquiry. Devereaux tells the others about Topaz, in order to provoke some reaction. JarrÃ© claims it is misinformation, and says that Kusenov died a year ago.
JarrÃ© starts to panic. He visits the leader of the spy ring, Jacques Granville (Michel Piccoli). Devereaux, Nicole, and Granville were close friends from their days together in the French Resistance. Granville tells JarrÃ© it was a mistake to say Kusenov was dead; the Americans will easily discover that JarrÃ© is lying. As JarrÃ© is leaving Granville's house, Devereaux's wife arrives to meet Granville, her lover.
Devereaux sends his son-in-law, FranÃ§ois, to interview JarrÃ©. Devereaux and MichÃ¨le rush to JarrÃ©'s flat and find JarrÃ© dead, a staged suicide. FranÃ§ois has disappeared. After being clubbed and kidnapped, FranÃ§ois managed to escape from his captors' car with an overheard phone number and his sketch of JarrÃ©.
Nicole tells her family, with tearful eyes, that the phone number is Granville's, so he must be the leader of the Topaz organization. Granville is exposed and then commits suicide (in the USA and French versions) or flees to the Soviet Union (in the British version).

Question: Which group is easily likely to discover Jarr was lying?
Answer: The Americans.