On the other hand, on a country level, countries generally do have enough guns and ammo to greatly limit any chaos coming over their border; uncontrolled immigration happens not because countries can't control it but because they effectively choose not to.

they don't have to stop the hordes, they just need to make sure the hordes know that their are easier places to forage than yours.

I wonder how long that strategy will work. Eventually society will reach a new "equilibrium" but how many less defended societies will succumb to the starving hordes before that happens.

I quote "equilibrium" because social structures never stop changing. What I mean is a relatively stable situation where most of the world is not invading the rest of the world. Our present situation is that the larger portion of the population is not invading the rest, though the present trend seems to be in the wrong direction.

Is that true? I mean, I figure worst case, small rural midwest communities that band together and shoot trespassers on site will be the best off.

I guess an army of thousands could take it over but my hope is that me and my gun toting farming community won't put up with invaders and invaders won't want to take their chances