I will rank it on countries visited twice or more:
Oceania -
Australia - Season 2, Leg 9
New Zealand - Season 5, Leg 10
Asia -
China - Season 6, Leg 11
India - Season 7, Leg 8
Japan - Season 18, Leg 3
Thailand - Season 1, Leg 9
Malaysia - Season 4, Leg 9
Indonesia - Season 19, Leg 2
Vietnam - Season 3, Leg 12
Singapore - Season 25, Leg 9
United Arab Emirates - Season 15, Leg 6
Bangladesh - Season 17, Leg 9
Cambodia - Season 13, Leg 6
Oman - Season 17, Leg 8
Philippines - Season 5, Leg 12
South Korea - Season 17, Leg 11
Sri Lanka - Season 6, Leg 9
Taiwan - Season 12, Leg 11
Turkey - Season 7, Leg 9
Africa -
Morocco - Season 10, Leg 10
South Africa - Season 2, Leg 3
Tanzania - Season 11, Leg 6
Botswana - Season 7, Leg 6
Namibia - Season 2, Leg 4
Zambia - Season 1, Leg 1
North America -
Canada - Season 5, Leg 13
United States - Season 1, Leg 13
United States (Family Edition) - Season 8, Leg 8
Mexico - Season 3, Leg 1
Panama - Season 8, Leg 5
South America -
Argentina - Season 5, Leg 3
Brazil - Season 18, Leg 11
Peru - Season 7, Leg 1
Chile - Season 23, Leg 2
Europe -
France - Season 6, Leg 7
Germany - Season 6, Leg 5
Italy - Season 4, Leg 2
The Netherlands - Season 4, Leg 5
Russia - Season 17, Leg 7
United Kingdom - Season 3, Leg 3
Austria - Season 18, Leg 8
Switzerland - Season 3, Leg 9
Spain - Season 10, Leg 11
Sweden - Season 17, Leg 4
Norway - Season 6, Leg 2
Denmark - Season 19, Leg 8
Poland - Season 11, Leg 8
Portugal - Season 3, Leg 4