Hello sir.
You can see the system description showing exploited or controlled when you view the system. Specifically selecting the "controlled" systems filter on the powerplay section of the galaxy map will show all of the controlled systems as big coloured circle blobs. Most will indicate whether they're being undermined or fortified if any of these events are taking place (shield and crosshair icons).
If you prefer not to use the filter then the basic powerplay overview filter will still indicate controlled systems easily by depicting them as a bigger blob bang in the center of the coloured zones of influence.
Hopefully that isn't too confusing. I just woke up. Haha.
