(Note: this is much longer than I expected. I recommend reading the last two paragraphs and returning to the beginning if you're still interested)
OK, so Jameson comes down on the historical rupture side of the Postmodernism debate, and highlights our new relationship (or lack of it) to the past as one of the essential elements of the new period. He cites the mass appropriation of past architectural, literary and artistic styles as one of the symptoms of this rupture, stemming from our inability to relate to history in as authentic a manner as was previously possible, and I think I am with him on this point, but I am having difficulty articulating, or finding where Jameson articulates, the difference between postmodern appropriation of the past and pre-postmodern methods of appropriation. For example, Classical Greek architecture was heavily appropriated during the Renaissance and the period following the independence of the United States, and this sort of appropriation has to be qualitatively different from its appropriation in, say, Cesar's Palace in 20th century Las Vegas for Jameson's thesis to stand, and I think it is, but I'm curious about the sources of this difference and whether they constitute a break with history of the sort Jameson proposes.
The first place I turned was one of Jameson's early definitions of pastiche as the "return of the past without affect". Insofar as revivals of classical architecture in Renaissance Italy or post-independence U.S. corresponded to a revival of interest in classical ideals, and Cesar's Palace or other postmodern appropriations do not correspond to any such affects, but merely refers to the kitschy exoticness of a 'pop-knowledge' of Greece, this definition seems to hold: postmodern appropriation is hollow, "speech in a dead language" (17).
However, In Jameson's first example of a nostalgia film, he cites affects of the 50's – stability and prosperity of pax Americana, naïve innocence of the countercultural impulses of rock and roll (19) – as the chief subject matter of American Graffiti and the films which imitated it. The affects of a previous historical period form the core of the work, yet Jameson seems to use it to the same ends as architectural pastiche.
Jameson later refines the crisis of historicity facing depictions of the past to be an inability to "represent the historical past' [the historical novel] can only 'represent' our ideas and stereotypes about that past (which thereby at once becomes "pop history")"(25). I question the degree to which this is unique to postmodernity. There does not seem to me to be a major difference between representing a stylized and idealized Classical Greece and an equally stylized and idealized 1950's America. The one difference that I can see is in the methods of their production. Both in the case of film and architecture, Jameson highlights the fact that postmodern appropriations strive to be 'indistinguishable from the real thing', that they use art-deco credits or simulated marble. In the case of film I think this testifies more to the role photography has come to play as a historical artifact than to a conscious break with the past – that is, as film quality increased over time, the 'look' of a film, even more than the technology and fashions depicted by it, served to date the scene, with the result that our idea of a historical period became bound up with depictions of it. Just as a filmmaker strives to limit the amount of contemporary slang in a movie set in the 50's, they will try to capture 'the look' of the era, and that look is invariably given to us by film and photography. The glossy 'look of the past', then, could be attributed to simple matters of believability rather than an obsession with a history we have been radically severed from. I think the same technological considerations can be brought to bare on architecture: part of the reason (not the only one) we treat the appropriations of the Washington D.C. differently from Vegas is that the former were built for the most part using the same methods of the Greeks, whereas the latter could be thrown up in a matter of months, permitting the simultaneous construction of a pyramid, a circus, etc.
Reading Jameson's analysis of nostalgia films, I wasn't entirely convinced they represented a new attitude towards history that could not be explained by the rapid evolution of our technology for representing it, and the effect this (historical) change has had on our understanding of history. I don't think these questions threaten Jameson's major theses. They do, however, call into question the degree of the rupture he believes Postmodernism represents, making it more of a rapid acceleration of older practices than a radical break.