Clearly if the Chinese stop propping up the dollar, the dollar drops dramatically against the Yen and the Euro, so the risk in other export markets is not substantial. That is, one cannot equate a decline of the US$ against the RMB¥ as a decline of all currencies against the RMB¥ when that same decline would remove the functional support of the US$ exchange rate.

No one is saying this.  If the China stops propping up the US dollar, the dollar will fall relative to the Yuan, and American agricultural imports will rise, while exports of finished goods to America will fall. This has problematic implications for China's export-oriented development policy and agricultural independence policy.

On the other hand, if China continues pegging to the US dollar, but the dollar declines in value anyway because of the continuing US current account deficit, this causes the Yuan to also decline in value relative to other currencies.  That's a good thing for exporters, which is why they do this, but it's not a good thing when trying to buy things, including investment in assets, in those other countries.  That's the self-induced paradox of China's unsustainable, export-led growth strategy.  It's a Chinese-caused economic problem, not an American one.