One country might be able to get all the hashing power but that doesn't necessarily equate to them being one collective entity. Most Chinese businessmen would still think of profits over any other things any day, though some of them might even submit to the orders of the higher echelons but for the most part, the former becomes true. Sure, they have the most hashing power, but still the tech is way too crude to perform harsh attacks that could disintegrate bitcoin at its core.