The death of Pyle as a result of Fowler's perfidy and hypocricy is an indictment both of western liberalism and of American foreign policy in general, viewed as hopelessly naive and destructive by Graham Greene in his novel of Southeast Asia.
The Quiet American was intended by Greene as a warning to the United States, which he viewed with intense disfavor and not a little of the aforementioned hypocrisy, about engaging in overseas adventures for idealistic and commercial [the combination of the two illuminates the author's perplexity] reasons. By portraying the American, Pyle, as a bumbling, naive, ["He never saw anything he hadn't heard in a lecture hall..."], ignorant idealist ["Innocence, Fowler says, is like a dumb leper who has lost his bell, wandering the world, meaning no harm. You can't blame the innocent...All you can do is control them or eliminate them."] while simultaneously plotting Pyle's demise with the less-than-humanist Viet Minh guerrillas, Greene is living vicariously through his protagonist. The impact of his novel is to offer both wise council regarding ill-considered adventurism in Third World countries about which we know little and to reconfirm the hostility much of the British Foreign and Intelligence Services held toward their former colonialists.
Greene's novel was published very soon following the French defeat at Dien Bien Phu and its grudging acquiescence to Vietnamese independence. As the United States moved in to replace the French in its efforts at preventing the fall of the southern half of the country to the communist forces of Ho Chi Minh, the British, who had a long history of colonizing Asia but who now were reduced to a lesser role on the world stage, look askance at U.S. foreign policy and looked down on the Americans' inferior "feel" for the less-developed world. As if its own crimes against humanity in the process of forging the world's greatest empire and the enduring legacy of European colonialism had not existed, Greene scathingly accuses the United States of making the world a less hospitable place to live.
The impact of The Quiet American resides in its prescience regarding the American role in Vietnam. In that, it is worthy of respect. In its own naivete, hypocrisy [Quothe Fowler: "I know the harm liberals do," while simultaneously excoriating the United States for crass commercialism and commercial interests that did not exist in Southeast Asia] and ignorance, however, Greene's novel proves as self-destructive as the policies he decries. The above quote ("You can't blame the innocent...All you can do is control them or eliminate them," which Fowler does by setting Pyle up to be assassinated) is every bit as prescient and hypocritical as anything Graham Greene/Fowler dislikes about America.