One possible goal for the story is to bring about a sense of nostalgia. As recounted in one biography, Irving was inspired by a conversation with his brother-in-law, and subsequently wrote the story in a single night. This, coupled with the nostalgic attitudes in the story itself, speaks to a desire to return to a previous time, when life was simpler:
The very character of the people seemed changed. There was a busy, bustling, disputatious tone about it, instead of the accustomed phlegm and drowsy tranquillity.
(Irving, "Rip Van Winkle," bartleby.com)
Although the necessity and morality of the war is not addressed, it seems that at least this town was not directly harmed by the British Monarchy, and (from Rip's example) could have continued in peace regardless of the ruler. Everything that was familiar is now strange; the change is irrevocable and Rip cannot return to his past. In the same way, the past of all humans is gone forever, anad can only be remembered, but the memory is often far more positive than actual events. Rip's (and Irving's) memories of the past are seen as better than the present, but not to any explicit effect; the ideal or the image of the past is desired, not necessarily the actual past itself.
Rip Van Winkle was included in a collection of short shories "written" by Washington Irving. Many of the stories, including this one, were not original, but adapted German folktales placed in an American setting. The point of the collection was to create American legends and myths.