Is Game of Thrones a Depiction of Medieval Culture or Just Current Day American Society?

One of the things that struck me while reading the Game of Thrones series was how well crafted George R.R. Martin's story world is. My interests as a writer are in capturing the essence of current social dynamics, but the characters and story lines in Martin's books are so compelling, they feel current, in spite of their medieval social structures, culture, and governmental organization. 

Besides, what is the difference between the donor class and the feudal lords in Game of Thrones anyway? Aren't the Koch brothers just modern day Lanisters? And I wonder some times whether Americans would care if our country really transitioned to a blatant feudal system, or a system of oligarchs, as many in my social network are decrying in the wake of the McCutcheon case. As long as most people can afford edible food like substances, cell phones, and tablets, is there a real threat of civil unrest in the U.S.? 

Martin's depiction of the importance of social order to a society is one of the strongest aspects of the Game of Thrones narrative.