Yet what she'd read about America in the papers intrigued her. No worrying about using the proper titles. Everyone was called a Mrs., Mr., or Miss. The American guests she'd met, like Mr. Camden, tended to be far less demanding than the English ones."
-- Narration (chapter 2)

Importance: One of the reasons that Sara is interested in moving to New York City to work for Mr. Camden is the lack of formality in the American culture. While this does turn out to be true, what is also true about American culture at that time is that there is still a significant gap between how mobile men and women are allowed to be in American society. Sara's largely informal relationship with Theo turns out to be both the greatest joy and deepest sorrow of her time in America.

It's far from subtle. I see it as a last gasp in an age of excess. Maybe...
-- Mr. Theodore Camden (chapter 7)