What you're talking about is something experts in the field call "public memory" or "collective memory", is used to describe a shared pool of information and memories of a social group, often times racial, religious, or national. This is an important factor to historians when they write history. It's also the same reason why primary sources, or first person accounts taken down shortly after an event usually have greater weight than first person accounts taken years or even decades later.

I'm not sure what online materials exist specifically for this. But one great resource that's a fun read is a book by historian Bart Ehrman entitled Jesus Before the Gospels: How the Earliest Christians Remembered, Changed, and Invented Their Stories of the Savior. Ehrman discusses and explores collective memory from about 2,000 years ago, examining the gap between what happened after Jesus of Nazareth died and 40 years later when the first gospel (Mark) was written down. He relies on modern scholarship around collective memory and psychology to understand how memory within groups can change over years, and it's truly fascinating.

Short answer:

The poet Lamartine remarked: "Napoleon's ashes are not yet extinguished, and we're breathing in their sparks". There is "history" as practiced by historians-- hopefully animated by some spirit and techniques of dispassionate inquiry into facts; and there is "history", the stories people tell themselves, a matter of nostalgia, memory and chauvinism, animated by symbols and belief and much less interested in inquiry. This latter "history" distinct from the "historians' history" -- is a worthy and important subject.

Discussion:

Nostalgia and memory are important to historiography-- that is "how history is written", how we understand it today, as opposed to "what it actually was"-- these can be two very different things. It's important to us both as a subject in itself, and as a filter that may have colored the writings of our sources (for example later Roman historians' enthusiasm for the Republic).

Let's take an example of a nostalgic but largely ahistorical trope that is nonetheless of great historiographic importance in the United States, the story of the Confederacy as the "Lost Cause". Not motivated by a search for "what happened", but rather a search to validate the nostalgia, memory and identify of a political constituency, the "Lost Cause" advocacy is a big part of our landscape of Confederate monuments in public places.

A historian of the Renaissance has to engage the [then] contemporary passion for antiquity, the reprocessing of "Roman ruins" into a new cultural identity and humanism. To be clear-- the history of Rome didn't have to be factual to stimulate the Renaissance; it's a nostalgia, an invented past that grows from ruins and histories, true or not less important than how it's understood.

A similar sort of process happens with Napoleon. At his death in 1821, Talleyrand -- admittedly not an impartial observer-- comments that its "not an event, just a bit of news", meaning that Napoleon's contemporary political salience is small. But in succeeding decades, nostalgia and memory overwhelm the experience of defeat and occupation, and Napoleon's legend grows. . . culminating in the "Retour des Cendres" (="return of the ashes") from St Helena in 1840. This wasn't the beginning of Napoleonic revanchism, but it is fuel on the fire. Casimir Delavigne, a nationalist poet who wrote the national anthem for the July Monarchy, wrote a suitably enthusiastic welcome home note for the Emperor's remains.

France, you have seen him again!Your cry of joy, O France,Drowns out the noise of your cannon;Your people, a whole people reaching out from your riverbanks,Holds out its arms to Napoleon

So an historian of 19th century France needs to engage not just "what did Napoleon actually _do_" -- but how did the French national identity process that history? There are decades of French historical novels that grapple with France's experience- Balzac and Stendahl, Victor Hugo and of course an endless parade of memoirs.

Similarly, someone trying to understand the history of the United States has to reckon with not just how the Civil War was fought, but how it was and is remembered.

What is available to read about memory and history? A lot of it is literary, which may or may not be helpful to you. For the Italian Risorgimento, for example, one thinks of Lampedusa, and particularly his novel The Leopard. Gabriel Garcia Marquez comes to mind for Latin America, Margaret Mitchell ("Gone with the Wind") for the US and the Lost Cause.

But for historians who've grappled with the historiography of nostalgic subjects, a very useful introduction is a short piece by Patrick Hutton that you can find online on JSTORHutton, Patrick H. “Preface: Reconsiderations of the Idea of Nostalgia in Contemporary Historical Writing.” Historical Reflections / Réflexions Historiques, vol. 39, no. 3, 2013, pp. 1–9.

Highly recommended - Hutton engages the subject of just how memory and nostalgia have come to be treated by modern scholars; he also notes that its not exclusively a historian's topic, referencing work by sociologists like Fred Davis' "Yearning for Yesterday", a kind of history of opinions about nostalgia as a sentiment.

I'd also recommend Ivan Morris "Tragic Heroes in the History of Japan" -- the Japanese have traditionally had a great appreciation for historical tragedy; processing what was in its own time a very real defeat and disappointment into something transcendent, as in failure of Saigo Takamori. Morris talks a lot about not just the historical events, but how they are processed by memory and nostalgia, and the significance that that nostalgia, as distinct from the actual event, had to later readers.

A useful contemporary analysis is Peter Fritzsche's Stranded in the Present (2004), with the subtitle "Modern Time and the Melancholy of History"; Fritzche has a nice line describing it as being "about our invention and possession of the past". It's worth finding in a library, if your subject is memory and nostalgia . . . well reviewed and thoughtful on the subject. Fritsche looks in particular at memory of the French Revolution.

As for the concept of memory, you may wish to look for a University of Missouri PhD thesis from the last five years by Dr. Terry Britt. It is from their journalism school. He studies this concept as it relates to journalism, history, and Memory. He currently teaches at the University of Texas at Tyler.