There are ~311 million people living in the USA, with 82% living in urbanized areas. One might define urbanization in the modern era as the distance to the nearest Starbucks. An "urban" environment would therefore be anyplace within a 20 mile radius. Yes, more than 80% of the USA (that's 250,000,000 people) live within 20 miles of a Starbucks.
Nicola Twilley focuses on the class issues at play:
Certainly, Starbucks density is often used as a gauge of economic vitality: Davenport links to research showing that in London, “for every 0.5 km a property is located from a Starbucks, the rent falls by an average of 20 percent up to 2.5km away,” and earlier posts on Edible Geography have discussed Magic Johnson’s seemingly successful Urban Coffee Opportunities initiative to seed underserved communities with Starbucks stores as a tool of urban regeneration.