You mistake NOT recognizing with Cancelling.

If you have a US citizenship, any other citizenship you posess will not be recognized. But, they do NOT have right to outlaw your original citizenship. You got that? It's a legal right from your original country, it's not something US has the right to deal with. They can only decide whether to give you a US citizenship. Most of the countries do NOT recognize multiple citizenship, but they all do it this way. But China is the only country, will outlaw your Chinese citizenship, whenver you have another citizenship. Basically, they are sending people away to other countries. Just use some common sense. What US cancel or outlaw was your greencard, because as a citizenship, you are no longer qualify for that.