We'll only go into nations and to people that invite us and only for specific things. For example, neither Nigeria or its neighbor Cameroon even though the Boko Harum is making life horrible.
And other nations and peoples have not invited us either, but we give them technical assist. The power plant that the Israelis blew up this past month will be rebuilt by American taxpayer dollars through a government insurance program. The Iron Dome money from us is not an offensive weapon, but it doesn't work well. If it did, the Israelis would lose their talking point for their latest actions. They'd have to face up to their failed polices.
As a member of NATO, we were called in to stop what was called genocide in Europe in the Nineties.
The Iraqi government asked us to do this, and so did Kurdish forces. We are not going to war, we are providing humanitarian relief and covering firepower to protect people from dying.
In a country our nation tore into pieces under Bush. It's the right thing to do in this particular case.
And yes, we will use our firepower when all else fails to do the job. It is the place that we were put into after WW2 by the Allies. They had reasons for all that evolved after that war:

Look who lost so many more people in that war. The Axis losses were only a fraction of what the Allies lost, yet we won that conflict. People think that means nothing, but it changed the USA from top to bottom. We were assigned the role by the Alles to keep the peace with military power.
Not a pretty job and it's been abused. We are moving away from this system every day.
The squalls against this very narrow and specific action that involves force and is being denigrated sound like something that Ron Paul would say.
In fact, I'm sure he's still selling the same line now.