What would happen if China told the rest of the world they're only accepting BTC?

I'm not an expert, so I won't even get into what my "theory" is on this, but I'm curious to know if an event like this is realistic & I wonder what the impact on the US Dollar/bitcoin would be if it did happen.

EDIT: For this hypothetical let's assume that China happens to hold at least 35% of the world's BTC supply.. This would give them the most to gain from BTC going mainstream & the least to lose from Fiat being devalued.