Please announce to us why U.S. companies as Google, Twitter, YouTube, Facebook can not enter the Chinese market? We need

As we know, many U.S. companies can not provide service to the chinese. As Chinese, we want to know why it happened ,why we can not use the facebook ,twitter, youtube like Americans?
We want to have the right as the people of other countries.
众所周知，许多美国公司并不能给中国人提供他们的产品或服务。作为中国人，我们有权利知道为什么会发生这样的事情。为什么Twitter，YouTube，Facebook这些产品和服务，中国人不能使用。
我们希望能拥有和别的国家一样的权利。