A while ago, I beat Cure Mode Bioweapon on MB in every origin that isn't banned with China HQ. And now, I ranked every single one of them in terms of difficulty, from hardest to easiest (in my opinion)
The tier list is ordered (the 1st country in any tier is the hardest one of that tier and the last country in any tier is the easiest country of that tier. Example: Turkey is the hardest origin in the Very hard tier, and France is the easiest origin in that tier).
I had a hard time ordering countries in Easy and Free tiers, some of the placements there are debatable. Also, East Africa is arguably harder than Iraq (even though I put Iraq higher)
Afghanistan and Pakistan are missing, they should be in "Banned by China" tier
Also, this tier list is only for a mobile version of the game (Cure Mode is harder on PC)
If you have any questions regarding the placements, fell free to ask them!