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The problem is China banning Bitcoin mining as that will essentially shut down all mining operations in China which consists of a majority of mining on the Bitcoin network.
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I bet the authorities wouldn't ban the sale of asics (at least initially) so many miners would dump them overseas if there was a hint of a ban - or an actual ban. While it wouldn't be a pretty process, over time the mining would spread out across the world. And as is probably obvious, that would be good to geographic diversity.