Factual error: The Douglas firs or Redwoods shown at the front of Longbourn (Groombridge Place) were not introduced to the UK before 1827, but the film is set in 1797.
Other mistake: When Darcy proposes to Lizzie notice the clock on the mantle does not change time. Nor does the clock change time when the Bennetts are discussing having the militia leave town.
Answer: In previews to American audiences there were lots of comments that it was not a good ending (not romantic enough) so they filmed an ending with Darcy and Lizzie kissing to make it more romantic. The ending in other countries matches the original ending of the book.