To compliment Samualdude's post on most difficult season, this thread is for seasons that seemed more like a gap year trip than competition.
Season 8 - This is a no brainer
Season 23 - Yes. If there's any issue I had with this season was that it visited mostly developed, first world countries. Chile is one of those South American with a more stable economy. You can say that theyve visited "poorer" European countries like portugal and Poland, but on terms of culture shock factor for Americans and travel infrastructure, there's not much of a problem. The only country that seemed a little challenging culturally would be Indonesia.
Season 3 - Too many European legs where racers can get by with English. Singapore-Malaysia is highly westernized and people speak English there. Little culture shock factor.
Season 2 - The period of a time spent in Australia and New Zealand. Appeared to be more of an adventure tour than anything else.