I don't know what the reasons for the rise are, but I bet it's largely driven by Chinese investors/speculators rather than anything happening in the US, but I think that is reported on less because it is not very visible if you're not based there.
Can you point to any evidence that Chinese money has been behind large share of 2017 Bitcoin purchases?
Edit: Also, I don't think the closure of the Chinese exchanges matters much since they can still buy Bitcoins, the exchanges just can't operate in China.
Edit 2: And my reason for the assertion wasn't any special knowledge of cryptocurrencies, but rather that there's lots of Chinese money pushing up asset prices in other markets, so I don't see why they same wouldn't be true of cryptocurrencies as well.