what is the quickest way for me to add the geo "All countries and territories" to a big number of campaigns?
I was looking into the Adwords Editor but couldn't find a solution....
Re: Geo targeting
Here's the explanation on how to add multiple locations using AdWords Editor with different versions:-
Also, if you have a huge list of campaigns and you want to make massive bulk changes, then you might consider requesting API for that. Here's the explanation on how to start that:- https://support.google.com/adwords/answer/2375503?hl=en
So, to target "All countries and territories", simply delete all existing geo targeting. You can do that in Editor on Locations tab.