I would assume its not only because a expected tax law in the US, since that would only affect US citizens. May be the drop is caused by more rumors about crypto regulations on a international level, as it already happened a week ago or so. Did you see, both Hive and Steem dropped about 35% (!) in the past 24 hrs. BTC "only" 10%.
It is a concerning developement anyhow, and it shows once again, that cryptos are far from being reliable currencies, but rather a high risk speculative asset.