It is not possible because resources are distributed all over the world across different nations. All nations need to trade in order to get the resources they need and it means that they are part of a global economy. What happens is that some countries are less connected and other much more connected, but none is isolated.
if they have alliances with any other nation (which they most likely do) then it is their duty to stay on the side of those they have an alliance with because their government depends on it as well
