From SUVs to Double Whoppers, Americans believe bigger is better -- and that includes Keira Knightley's breasts.

The British big-screen beauty's modest bosom was supersized in the digitally altered U.S. publicity photos for her 2004 film "King Arthur."

She said this week she was dismayed when movie marketers decided her natural A-cup chest could be no less than a bouncy C in shots of her as a leather-clad Guinevere.

"Those things certainly weren't mine," she said in an interview with BANG Showbiz news.

"They said, 'We want to make them slightly larger, and you'll get approval [of the photos].' And I was, like, 'OK, fine. I honestly don't give a s--t.'"

While Americans saw the A-cup actress' chest inflated to the size of the Grand Tetons, British filmgoers saw the unaltered version of the same publicity photo.