Yes, China can have a real say on the price of BTC and more.
Should we be worried? I don't know if that worries you or not.
I personally think Bitcoin should not be controlled by any entitity but it's Bitcoin's fault to some degree.
It should have an algorithm that allows mining easily all over the world by anyone, not mega mining farms.
I agree on the notion that mining should have not been so centralised, the way it is now with asic devices. The years before were much more
fair to the average person, but theres no turning back now. Even if we wanted to, the large scale players on the mining race would not allow it.
But i still dont think it means that China has bitcoin in its grip, it more as if they have kind of unfair advantage over the rest of the world, for now, that is.