I have to start my story by outlining what I consider to be the context of your discussion. You say you want to look at “avant-gardes from the decline of modernism to the rise of globalization, 1956-1986″. It is not clear to me whether these dates were chosen because of turning points in the artworld or turning points in the world political arena – perhaps both.
Your background text lays emphasis on the large number of authoritarian regimes that existed in various parts of the world at the beginning of that period and presumably fewer towards the end. You talk about the rise of globalization, presumably towards the end of that period. The shift you want to discuss is very real, but let me offer you a slightly different set of temporal cutting-points to illuminate this story – 1945, 1956, 1968, 1979-1980, 1989-1991, 2001-2003, 2008-2010.
1945: This was of course the end of the Second World War. More important, it was the end of an intense 30-year-long struggle between the United States and Germany in their efforts, begun in the 1870s, to succeed Great Britain as the hegemonic power of the world-system.