> 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.