Actually the BRIICS have started the process for removing the USD as reserve currency and have also initiated a cash swap plan to protect against the devaluation of the dollar.
But all said, Yes, China is more exposed given the investment in US infrastructure and debt..so if things were to collapse in the US then China and a lot of other Asian countries will be affected with exposure remaining the sole criterion for the impact.
As for Chinese economy, given that the figures so far present a contradictory picture, not sure how to read it and to add to the mix, most of the stats released by the government is heavily regulated, read: only the officially approved stats are released..