How does the inn reflect the political and social changes that have taken place in the country as a whole?

Politically, the inn obviously represents life before the American Revolution and life afterwards.  In the narrator's first description of the inn, he points out the

"rubicund portrait portrait of his majesty George the Third" (Paragraph 13),

demonstrating that before Rip's "deep sleep," the colonies are still under British rule.  When Rip wakes up and eventually resumes life in the small community, he returns to the inn where

"instead of being a subject of his Majesty, George III., he was now a free citizen of the United States" (Paragraph 61).

Irving's description of Americans no longer being under the yoke of despotism parallels his discussion of Rip no longer being under his wife's domination.

Socially, changes also abound.  The inn once represented a place where Rip sat and listened at the feet of the inn's patriarch (Paragraph 14), but after 20 years, Rip is considered a patriarch. Rip takes Nicholas Vedder's place at the inn door, where he

"was reverenced as one of the patriarchs of the village, and a chronicle of the old times 'before the war' " (Paragraph 61).

America, a brand new country, is looking for its history, and so Rip seems to now have a place in society as one who can remember what life was like under British rule.

Finally, another social change is the freedom that Rip experiences because of his wife's death.  This metaphor represents the freedom that Americans felt after being out from underneath British tyranny.