I think the advent of short-short fiction is a big change. These stories move from the longer, drawn out stories and jumps right into the conflict. Jemima (sp?) Kincaid wrote some quality pieces. In addition, Raymond Carver wrote some excellent literary pieces that are studied in my college literature classes. Episodic fiction and hypertext stories are also recently added genres.
You have asked a massive question! The other editors have done an excellent job in highlighting the major aspects of the changes during this period. I would only want to highlight again the importance of minority voices being brought into mainstream literature - certain "classic" authors that you would expect to be studied are also now studied alongside other minority voices who traditionally do not fit the picture of American literature (whatever that means). Thus literature produced by immigrants for example (like Amy Tan) and other postcolonial voices have been rightfully given the due prominence that they deserve.
You have a lot of really insightful comments to think about. I'd only add the idea of the "underground" movements on college campuses in the '50s and '60s. Not only were students writing their own works in nearly every literary and journalistic form. Works like Lord of the Flies were circulated and taught as counterculture literature; and works like Their Eyes Were Watching God were brought back into prominence on college campuses across the country. It's not surprising that such a movement existed given the times and the culture so ably outlined by my colleagues.
After World War II, American literature reflected a guilt and disillusionment in the American dream. For writers like Ernest Hemingway there was a nothingness out of which man had to carve his own existence and find his own "clean, well-lighted place." In this malaise that arose from the aftermath of the atomic bomb, writers such as Joseph Heller wrote about the corruption of the military bureaucracy. His black comedy, Catch-22, captures the disillusionment of the citizenry with the government and its unconcern for the individual. And, with the threat of Communism and the "Red Scare," certain works, such as Arthur Miller's play, The Crucible, reflected the hysteria that can overtake a nation, as well.
Then, of course, in the 1960s there was much social protest literature. At the forefront of this genre were African-American poets and other writers such as James Baldwin with his Go Tell It on the Mountain and other works.
The previous thoughts about the expanding of the American canon were well conceived. Indeed, I think that as post World War II became more driven by the voice of the dialectical “other” in social and political realms, the experience of literature reflected this. The emergence of previously marginalized groups became something that was seen in literature, as well. As post World War II, American Literature sought to examine the social conditions that existed, I also think that a critical lens was applied to the foundations and premises upon which the country functioned. We can see this in works like Sallinger’s “A Catcher in the Rye,” or Hansberry’s “A Raisin in the Sun,” or Kushner’s “Angels in America” as three examples of a larger configuration. Works such as these critically assess both what it means to be America and also call into question what was considered to be standard practice. At the same time, it becomes quite clear that American Literature that follows after World War II seeks to question this reality as to why it is constructed the way it is as well as demand a type of transformation of it. No better is this seen than in the works of Arthur Miller, such as “The Crucible” and “Death of a Salesman.” These art samples do much of what American literature after World War II attempted to do in terms of identifying what is present and seeking to transform it into what can or ought to be as opposed to what is.
Well, this is a big question. I would start by pointing out that the American literary canon (the authors we consider worth studying) became more open to the voices of so-called minority groups. Literary works by African-Americans, Native-Americans, Jewish-Americans, Latino and Asian-American as well as by women writers and gays and lesbians are now firmly established within the American literary canon.
Another important change that I would point to is the shift from modernisn to postmodernism as a prevailing cultural mode. Contrary to modernist authors who tried to make sense of chaos, postmodernists like Kurt Vonnegut, Don DeLillo, Thomas Pynchon, Ishmael Reed embrace the apparent depthlessness of our contemporary world. The modernists' search for a unifying meaning out of the fragments of modern existence is mocked by postmodernist authors who make irony, play and the lack of ultimate meaning characteristic features of their works. Postmodernism literature also calls attention to its own artificiality through metafictional devices and pastiche (a technique that mixes high and low literary forms or conventions from literary genres).
After World War II American Literature underwent quite a few radical changes. This was largely because of the paradigm shift that took place because of the advent of the new Post Structuralist theories. Post Modern and contemporary critical theories began to question the very nature of literary language and concluded that there is no difference between literary language and ordinary language spoken by the lay man. Consequently, the very nature of literature and literary texts to be included in the academic discipline underwent a radical change. Film studies, advertising, and various other aspects of culture came to be included in the literature curriculum on American university campuses, with the result that quite a few of these Departments came to be renamed as 'Cultural Studies Departments.'
This of course meant that new and virtually unheard of writers came to be included in the regular curriculum of the American Literature syllabuses.