> By that reasoning, murder, robbery, etc., all exist everywhere, so clearly the existence of police forces doesn't prevent them
Right, to justify police forces you have to actually show that they don't cause more crime than they prevent, and by a big enough margin to make it worth the trouble.
> you might consider acknowledging that the U.S. — for its own mixed reasons, to be sure — provides the key support for an international rules-based order that, on the whole (and with tragic exceptions), has allowed billions of people to live better lives than they would have otherwise.
Every gang chief or warlord (including some of the examples you specifically picked out as bad places to live) makes that kind of argument.
By that reasoning, murder, robbery, etc., all exist everywhere, so clearly the existence of police forces doesn't prevent them — so sure, let's get rid of the police and other law-enforcement agencies. (Or more succinctly: Half a loaf ....)
> I'll take a world where my country has to pay for our own defence, even if it means higher taxes for me, over one where US personnel can kill someone like me and the US will give them a getaway flight with no repercussions.
If you can make such a world happen, you're of course free to do so. Until then, you might consider acknowledging that the U.S. — for its own mixed reasons, to be sure — provides the key support for an international rules-based order that, on the whole (and with tragic exceptions), has allowed billions of people to live better lives than they would have otherwise.