I noticed an angle could work for one geo and fail for another, same for landers / ad copy etc.
my questions are
1) how common is it that a different country will respond significantly different to landers/angles
2) when you test a new geo, do you start from scratch with your top 3 angles from other geos?
Maybe it seems obvious to you, but it's new for me 
Honestly for me very rarely one angle worked in one country and tanked in another.
The thing I've noticed is that it changes more with race.
For example for dating offers in Asian countries images of asian girls really made a big difference.
And yes if you test a new geo I would first test what you already know that works.