Churning like a third-world traveler's stomach

Churning like a third-world traveler's stomach, Incidents of Egotourism in the Temporary World is a travelogue about finding the unexpected in familiar places. A frustrated shipper of rare books at a Boston bookstore (who refers to himself as "The Egotourist") returns to his parents' suburban New Jersey home to work temporary jobs and earn enough money to take 100 buses to Cuzco, Peru.

Alternating among essays, dialogues, and short spiels, Incidents of Egotourism in the Temporary World rolls with the Egotourist's restlessness as he tells of long-distance love, Black Sabbath cover bands, flirtatious administrative assistants, minotauric secretaries, and camaraderie in copy centers, all of it heading toward a hard-earned trip south of the border. Ultimately, the Egotourist discovers that what he sought in far-flung destinations is just as easily found in the unexpected exoticism of home.

Could you please explain to me the emboldened parts?

Though I know "if our stomach is churning" it means "it is nervous", but I wonder what here "third-world" and "churning like a third-world traveler's stock" means.

Source : http://www.betternonsequitur.com/index.php?egotourism