Does anyone know how each season is being planned? Sure, its understandable that the production would only visit countries that are not affected by political and environmental unrest.
Is there a recurring theme for each season?
I like how teams travel to various countries or cities that has some relations to the previous country they travelled to. For example, in Season 18, teams visited a tea shop in China and has to drink and remember the flavour of the tea so that they could guess the right cup at another tea tasting venue in India. Its kind of cool that we learn that tea was one of the main exports between Kolkata and Kunming.
In Season 19, the starting point was at a Buddhist temple in California, which is affiliated to Taiwan's largest Buddhist organization. And soon enough, teams would jet off to Taipei and take part in another challenge in a (Buddhist-Confucian) temple. The 3 Asian countries featured in Season 19 had a challenge that took place in a Buddhist temple. Hence, the start of Season 19 had a religious/spiritual theme.
After visiting Japan in Season 20, teams arrived at Hawaii to perform a task that is commonly practiced by Japanese immigrants in Hawaii.
My Speculations are as follow:
Season 7 - Members of the British Commonwealth and Latin America. Almost every country they visit is either related to the british commonwealth or a Spanish speaking nation. The only country visited that is not part of any of the above is Turkey.
Season 10 - Asian Nations/Empire colonial franšais - They visited every part of Asia (East Asia, Northern Asia, Southeast Asia, South Asia and Southwest Asia), not forgetting that they also visited places like Mauritus where there is a large Asian population as well. Many countries visited had a French Colonial background (Vietnam, Mauritius, Madagascar, Morroco and of course, France).
Season 12 - Season of the little countries. Many countries visited in this season were rather small in land mass, and often being overlooked or passed off as part of another country.
Season 13 - Communism/Warriors - Russia and Kazakhstan (both part of the former Soviet Union), Cambodia (once controlled by the Communist Khmer Rouge). This season also featured a number of tasks in Warrior/Military like places - Maori Warriors of New Zealand, receiving a clue from a trained Golden Eagle from Mongol Warriors, taking part in detours located in a Russian military camp.