To clear all threat in territories you need to find all scarecrow posts, sniper posts, camps and mine fields, all mark in red colour except the camps.
Most of them you can find them while searching for scrap and exploring 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 threat locations you need.http://www.gamepur.com/guide/20279-mad-max-where-find-minefi...
I hope that helps! Good luck.