Hi Brian -
China should not be thought of as a communist country, but rather as a business country. They have no interest in bringing the Americen economy down; it would be bad for business in general, and specifically, bad for the Chinese economy. Do not worry about this.
If the USD falls, it would in fact be good for the US ecomony in that US goods would become more competative internationally, as well as making imports more expensive. I suspect that this is what Washington secretly hopes will happen.
Of course for political reasons they can never admit to this!