What would you do? "If an occupying force were in the United States and killing innocent civilians to go after perpetrators of on-going war crimes, would US citizens become more radicalized, especially when their homeland is being invaded and families are being brutally maimed and murdered?"
A: I believe I would do what most people would do in every country: respond with guerilla warfare. John Ross has excellent work on this idea in his book "Unintended Consequences." Of course, each nation tends to bring their own world-view to "guerilla warfare" ...which is a huge problem in the uncivilized, theocratic areas of the world.

The problem is complex, but I strongly believe we should postpone involvement in the middle east until we have individually-targeted "leading force technology." At that point in time, it would be a good idea to kill the mullahs of Iran, and supplant their government with a free state. See: http://www.vice.com/read/busy-gallows-of-iran-513-v16n1 --Theocracy/totalitarianism spreads by means of its disseminators who are considered "most legitimate."

I favor the rapid development and deployment of K. Eric Drexler's "leading force technology" for precisely this reason. This would allow the west to reduce "collateral damage" to zero. However, if it's not deployed by voluntaryists, it will likely doom humankind, so let's try to prioritize that. See: http://e-drexler.com/d/06/00/EOC/EOC_Chapter_11.html#section04of05