The fact that the husband and wife are the only Americans in the hotel draws particular attention to their nationality. Hemingway is putting them in a context where they are the most American thing since Wonderbread. We can't be sure why they're here—maybe a honeymoon, a trip, or the husband's work. What do you think? Their drifting state also helps us see the importance of their marriage: being a wife is the only identity the woman seems to have. While her husband may have his reading (and may choose to listen or not listen, care or not care), the wife is simply waiting, as if she's dependent upon his movements, desires and decisions. Or, at least, she seems to be.