Here's the reality: The United States (and looking at these situations, it's generally the US which provides the majority of troops, equipment, and funding for these kinds of operations) just flat out does not have the resources to fix the world. Not and still maintain our own domestic welfare programs and try to maintain the peace in our own cities.
We just don't.
Just
trying to pacify Iraq and Afghanistan has worn us out, and we didn't succeed. You CANNOT pacify a country whose people need a (brave and incorruptible) police officer watching them 24/7 to prevent them from raping, murdering (and perhaps eating) their neighbors. After WW2, we were able to occupy and pacify Germany and Japan, but we were only able to do so because those two societies had law-abiding, orderly cultures.
And now we import the pathologies of the rest of the world's cultures into our own. The
UK Telegraph reported in 2009:
UK is violent crime capital of Europe
The United Kingdom is the violent crime capital of Europe and has one of the highest rates of violence in the world, worse even than America, according to new research.
Although homicides are lower than the US, the UK's current violent crime rate (robbery, burglary, assault, etc) is much higher than the US rate.
I don't think the UK was that way 40 years ago.