There have been security concerns about sharing space technology with China, versus with Japan and Europe. Russia is also not highly trusted, but on the other hand their space technology is regarded as equal to ours, so there's not much security risk to cooperation.
Probably moving forward, China will move into the top tier of space powers alongside Russia, the U.S., Japan, and western Europe, and ahead of India (which has its own program albeit with a lower budget).
At that point, cooperation between China and the West would be mutually beneficial. One thing China brings to the table is a very low cost program; they seem to be able to do launches for one tenth the U.S. budget.
Probably moving forward, China will move into the top tier of space powers alongside Russia, the U.S., Japan, and western Europe, and ahead of India (which has its own program albeit with a lower budget).
At that point, cooperation between China and the West would be mutually beneficial. One thing China brings to the table is a very low cost program; they seem to be able to do launches for one tenth the U.S. budget.