To clear all threat in territories you need to find all scarecrow posts, sniper posts, camps and mine fields, all mark in red color except the camps.
Most of them you can find them while searching for scrap, or can be revealed from the balloon outposts.
Some of them though can waste loads of your time, especially the minefields.
Below is the link for finding all treat locations you need.http://www.gamepur.com/guide/20279-mad-max-where-find-minefi...
I hope that helps! Good luck.