In China, once you become a monk or nun, you can practice any Buddhist tradition. You are not even limited to Chinese Buddhism. You can practice Theravada Buddhism, Tibetan Buddhism, or any other tradition. This is not the case in Japan. When you join the Sangha in Japan, you choose whether you want to be part of the Zen sect or Pure Land sect. I'm not sure this is such a bad idea. In China, it is so easy for monks and nuns to dabble with different practices that many of them never advance far in any one tradition. It is like what I say about changing meditation methods all the time. You never get anywhere. It's like window shopping.
Let me close by saying a few things. The few years I lived in Japan I spent studying and practicing. I didn't make it a point to analyze the similarities and differences between Zen and Ch'an. Likewise, my contact with American Zen centers and with people who follow the Zen tradition in the United States has been limited, so everything I have said must be considered in this light.
Furthermore, we have limited our discussion to China, Japan and the United States, but there is also a strong Ch'an tradition and practice in Korea, called Son, and masters from Korea have come to the United States as well. My guess is that in each of these places, the tradition of Ch'an Buddhism carries qualities unique to those areas and environments. A basic principle of Buddhism states that all things change. Why should the different Ch'an traditions be immune to this fundamental principle?