If you kill an American, you too should die after you have seen your loved ones die painfully.
THAT THEY WILL UNDERSTAND.
Sure, the technique works, and it's pretty up front and personal, but don't we prefer "carpet bombing" if we can get it?
Anyway we now have a sonic pain weapon that can drive people away from places without killing anyone. Just pursue this technology; build really big ones; chase these people, their friends, their neighbors, their foreign help out into the desert. Then destroy all their stuff!
That leaves the oil in the ground nice and safe for our later use.