Myanmar is also a possibility.
The problem seems to be two-fold, maybe three fold. Some nations remain on the State Department Travel Advisory list, including some places TAR US has visited in the past such as Libya and Ukraine, for example. Other possible countries have become safer, but there may be concerns about being able to produce a leg ar two in those countries.
The second problem is have local production staffing available, TAR has not been to much of Africa since the death of a local producer who was based in South Africa and was in Kenya making production arrangements for another show a couple of years ago. That may be one reason why central and southern Africa have not been utilized in recent seasons.
The third reason may be that TAR US has become reliant on national tourism ministries and agencies to help arrange locations and tasks in order to facilitate being able to film in those countries.
One has to remember that all of the contestants and many of the traveling production team travel on US passports, and have to meet any local visa and other requirements imposed on US originating travelers. There are countries that impose more rigid requirements on US passport holders because of the post 9/11 security measure imposed by the US on nationals of certain other countries.
The other thing is that even when an area had settled down, the producers tend to wair a couple of years before considering those countries for future races. (Sri Lanka and its civil war only ended a couple of years ago, for instance.) And then, there's now the Sharia problem in some Islamic majority countries, and the anti0GBLT legislation in Russia and some African nations. The rigidity of these new laws also may make it difficult for TAR to plan to go to those places for the foreseeable future.