China had never had to deal in a world of countries of approximately equal strength, and so to adjust to such a world, is in itself a profound challenge to China, which now has fourteen countries on its borders, some of which are small, but can project their nationality into China, some of which are large, and historically significant, so that any attempt by Chinese to dominate the world, would involve in a disastrous for the peace of the world.
I think zombies are the great analogy for all of our fears about all of the scary things that happen on our planet, and the potential for scariness on our planet. Being chased by anyone or anything can be scary. It is just a big, fun analogy.