It's not economically optimal for one country to manufacture all the jewelry and its neighbour all the tanks, because this situation quickly becomes one country
> because this situation quickly becomes one country
i would argue this to be a good thing - a global "country". And yet, it is the human condition to separate tribally. It's why civilization can't advance more, until this becomes solved.
good thing we have more than two countries. in history, the jewelers generally tend to win because they just pay off some other tank building country - see Kuwait, for instance