The key before and after difference in the story is that Rip goes to sleep a citizen of Great Britain and wakes up a citizen of the United States. In the twenty years that Rip has been snoozing, the former colonists declared their independence, fought a revolution, and established their own nation. Showing the difference between the two times is the whole point of the story.
The town before the revolution, the place Rip knows so well before he falls asleep, is a drowsy, quiet, apathetic place. The men gather in front of the inn under the portrait of King George III and talk about news that is three months old. They have no sense of themselves as participants in the life of the nation. They have no sense of agency.
In contrast, Rip comes back into a town invigorated and energized by being part of a democratic republic. People have a voice: they have representation. They can vote and elect their own officials! Apathetic, happy-go-lucky, unfocused people such as Rip have no place in this active and enthusiastic new world where independence has changed everything for the better. In writing this story, Irving is participating in myth-building about a new nation.