I think the "world police" argument is self-defeating.
First, nobody - even the most ardent interventionist - has ever asserted that the US should send its military to (some godforsaken shithole (GSFH)) because "we're the World Police!".
Suggesting such is prima facie untrue. The only people that even use the term are ironically usually the political left who, if they had their druthers, WOULD enable just such a thing likely under UN auspices. So it's not even the "world police" thing that bothers them, it's that we're pursuing our own interests, because they're presumably too stupid to recognize that every other state on the planet is doing the same thing to the best of their ability. So their real argument isn't that we're acting like "world police" so much as a basic argument against our own success....and that devolves, folks, to simple self-loathing.
US involvement in GFSHs is based on US interests, full stop. Setting aside the public pap of WMDs, it's clear that we went to war in Iraq to protect OIL, because after air, and water, and food, oil's pretty much the most fucking important substance on the planet.
Now, we can argue priorities, cost/benefit, direct self-interests vs enlightened longterm self interest, etc all day long. I might even agree with you on some points, despite our likely opposite political dogma.
But the crux of geopolitics is that EITHER:
- you pursue naked Realpolitik, and act ONLY in your self-interest, or
- you pursue a humanitarian policy of trying to "do good" where you can.
What the naive don't seem to understand is that you don't get to "not play". It's not a choice. If millions are being slaughtered in Rwanda, action OR INACTION is making a statement about US interests, values, and cost/benefit calculations, upon which then other states will plan their expectations about our behavior.
And FWIW, the second policy pole listed above? It's far, far more blood and treasure, intervention, and judgemental side-picking, 'warmongering scumbaggery' than the former.
Basically: grow the fuck up. The world's more complicated than you apparently understand.