Well, Guías turísticas de América is a good term to search, but it's not the only one. For example, if you tell that to an employee, he may give you a book on Perú or Argentina.
I am sure you can ask a more specific question, like asking for "Seattle" and, if the attendant doesn't know it or isn't familiarized with the pronounciation of the word (many of us know the word but we pronounce it like it would sound in Spanish "sitel" whereas you say "siidel"), then ask for "una guía de los Estados Unidos".
An even more complete bookstore is Casa del Libro, in Gran Via, close to the metro of the same name, very downtown.