Our current political culture is based on different parts of our countries history. If you look at each President and their policies and ideas they are generally based off of one of the great Presidents of the past. As someone else has already mentioned, Lincoln, JFK and FDR are still influencing our current political culture.
Go back to the founding fathers and examine our earliest documents of government to see how we are still defined by those principles and ideals. The Constitution of the United States defines the roles of the branches of government and their duties and responsibilities. Even though there have been amendments and judicial interpretations to the document, its core is relatively unchanged in over 200 years. It is a remarkable piece of our history that continues to define what it means to live in the United States of America.
I think most Americans, knowingly or not, believe in American exceptionalism. That is, they think that not only is America different than most countries, but that it is somehow better, both unique in the history of the world and full of opportunities you can't find anywhere else. Not sure I buy that, but I think our history, and the political culture it has created has helped to convince many Americans of this.
I think that the '60s made our political culture look the way it does today. We got the culture wars that we have now because of the split between the counterculture and more traditional Americans. We have the fights over government spending because of LBJ's efforts to create the "Great Society." Our political culture that is so adversarial and so polarized comes largely from the splits that we experienced during the 1960s.
U.S. history explains the ardous path the country made on its way to the twenty first century. Perhaps President George W. Bush said it best in his inaugural address:
We have a place, all of us, in a long story; a story we continue, but whose end we will not see. It is the story of a new world that became a friend and liberator of the old. The story of a slave-holding society that became a servant of freedom. The story of a power that went into the world to protect, but not possess; to defend, but not to conquer. It is the American story, a story of flawed and fallible people united across the generations by grand and enduring ideals.
U.S. History explains our struggle to establish a government comprised of diverse geographical areas and people with diverse interests; our struggle with slavery and the attempt to guarantee rights to every person. One cannot truly understand the political culture of the U.S. until one understands its history.