Which edition of the Joy of Cooking did you order, Ray?
(Envying your vino-gastro tour...)
US cooking was a great deal more regional before the unifying/homogenizing forces of national media and marketing (which really picked up speed in the 1920s with radio), the automobile (1920s likewise a big turning point), the 1941-45 war, and then television and the interstate highway system. The relentless growth of industrial farming and food processing is the dreary backdrop to counter-trends (vegetarian, organic, and whole-food cooking,"ethnic" food and ingredients, and local sourcing).
Apart from and alongside the gradual integration of immigrant cuisines in different areas of the country, U.S.ians were introduced on a really national scale to authentic cookery of other cultures starting with Julia Child, continuing through the 1970s and into the 1980s with Marcella Hazan (Italian), Paula Wolfert (Moroccan), Madhur Jaffrey and Julie Sahni (Indian), and a collection of Chinese cooks (Virginia Lee, with Craig Claiborne; Irene Kuo; Gloria Bley; and Wonona Chang).
Ina Garten had important forerunners in the 1980s and early 1990s: Lee Bailey, the Silver Palate duo of Sheila Lukens and Julie Rosso, and of course the empress of 'lifestyle', Martha Stewart, who did a lot to encourage and promote Garten early on.