What I'm referring to here is idealism [1]. Whether it's European colonial powers or the US, the basis for foreign intervention is, quite simply, that we are the Good Guys. Why? Because we're the Good Guys. Even slavery was justified in Christianity by converting the heathen and saving their immortal souls, a fundamentally idealistic argument.
What's the alternative? Materialism [2], the premise of which is that there is not anything metaphysical that defines "goodness". Rather, you are the product of your material circumstances. There is a constant feedback loop if you affecting your material surroundsina and those surroundings affect you.