I guess china will be the first country to ban bitcoin officially, since Chinese government own their central bank, they don't want another competing currency disturbing their money printing business. But if US government officially support bitcoin, they might just follow
I'm not so sure about this. China CB as been buying gold (massive amounts in the last few years) whereas the US has been selling, and we don't even know that the gold the US claims is in their vaults is really there (they defaulted on Germany's gold last year when delivery was requested.) Gold is not something CBs buy en masse when they are interested in saving their rapidly inflating fiat currency at all costs. In fact China has recently made statements expressing interest in an entirely new currency standard and their gold purchases may be to help back such an endeavour.
Also, bitcoin may be very important for money laundering by high chinese officials. And we know how rampant corruption is over there. (I lol because it's rampant over here too, although it's a bit harder to bribe the zoning board for a ruling exception in the US so maybe it's not as prevalent in the lower levels.) Sure, they could make it illegal for the general populace yet find ways for these officials to launder.... OTOH, with the chinese public participating, price is increasing (and possibly less volatile) which makes it a more efficient vehicle for laundering. Officials may be dragging their feet due to their own [laundering & gambling] self-interest.
I think the chinese goobermint did issue a statement a while back that bitcoin is, in fact, illegal there. They don't seem to be enforcing this, so IDK what that says about its actual legal status...
Also there was that suspicious TV docu on the state channel... they don't just let "big advertisement for bitcoin" air when they are planning on dropping the anvil on it. Something fishy's going on.
Also, while bitcoin could certainly bite the Chinese government and the Yuan, it would bite the USG/USD even harder and we all know how much the chinese wants the US on their knees.
So while they may crack down on bitcoin, it may not be as quickly as we'd expect from a western government, or with the fervour that we'd expect.