I don’t think Anthony Bourdain specialized in any one cuisine. He graduated from the Culinary Institute of America in 1978 but he did not publish his first cookbook until 2004. This book was titled “Anthony Bourdain’s Les Halles Cookbook: Strategies, Recipes and Techniques of Classic Bistro Cooking”. It supposedly “teaches you everything you need to know about cooking classic French fare.”
However, Bourdain is better known for exploring international cuisines. Another book he originally wrote in 2001 called “A Cook’s Tour: In Search of the Perfect Meal” was reissued in 2002 with the title “A Cook’s Tour: Global Adventures in Extreme Cuisines”. So, if anything, Bourdain specialized in exploring all cuisines.