This is true. But what happens next? A collapsed power structure is not a nice place to live. Someone has to deal with crime, resources, arbitration, and taking out the rubbish (qv http://www.luton-dunstable.co.uk/Luton-ISIS-recruit-Abu-Aziz... ). So another person steps up to fill that role. Unsurprisingly, he has to deal with the power structure of the region that he finds around him, so he makes deals; and he has to deal with bandits, so he makes a militia. Until he makes his way to the top of the US kill list, perhaps by phoning the wrong person.
"Local warlord" is a position, not a person. The replacement for warlordism is an accountable rights-respecting impartial justice system. Nothing less will do. You can't deal with injustice by committing more injustice. You can't eradicate violence with more violence. This isn't a Clint Eastwood movie, you can't just ride in, shoot some designated bad guys, and ride out again with everything fixed.
Also, would the US rather have an anti-US warlord who deals fairly with his own people or a pro-US one who is corrupt? The treatment of Latin America shows quite clearly that they'd prefer the latter.
Unfortunately as soon as you say, "So let's apply justice to the middle east", you trip face-first over the Palestinian question.