Another theory: Americans fears most of the world, including socialism.
no, its not a joke. see middle east, terrorist, china, socialism, Kim Jong-un, the list goes on...
The US government attempts to instill fear in it's people to use these things as an excuse for it's actions. Those actions are not in the best interest of the American people, nor are they intended to be.
I'm an American and I have zero fear of terrorists, Arabs, Chinese, Socialists, North Koreans and the list goes on. I DO fear my own government however, because they're capable of nearly anything at any time and they do not care about the laws that are in place to keep them in check(Constitution).
You are in error when you attribute the actions of the rogue American government, running around the globe murdering people(including Americans), to the American people. Most Americans either haven't a clue what's going on or do not support DC's actions. For evidence of this check Congressional approval polls.