Imagine if another country threatened to cancel an American company unless they merged with a local firm and paid a one-off bribe to the government.
Only certain sectors in China have joint-venture requirements. Over time, more and more sectors are being freed from those requirements. These sorts of regulations are allowed for developing countries under WTO rules.
You cannot do business without a local partners in many industries (read: a "joint" venture in which the local "partner" will acquire your IP and eventually compete with you down the road). Foreign ownership is restricted. It was big news when China mildly liberalized its laws earlier this year and only as a gesture in the ongoing trade disputes.