Is BitCoin controlled by China? Recently, the CEO of Ripple stated that more than 50% of the BitCoin miners are in China, therefore, were the Chinese 
government to interfere, they could control BitCoin (I assume via a 51% attack, I didn't check details).

"“I’ll tell you another story that is underreported, but worth paying attention to. Bitcoin is really controlled by China. There are four miners in China that control over 50% of Bitcoin,”"

Is it true that 4 Chinese miners can control all of BitCoin?
Here is Blockchain.info's chart showing the current estimated distribution of the bitcoin network's hashrate.

Keep in mind: some pools are composed of many individual miners, so in the event of an attack, those individuals may simply redirect their hashpower to a different pool that is not involved in the attack.

In general, controlling the hashrate is not equivalent with 'controlling bitcoin'. If a single entity got control of 51% or more of the hashpower, then they could launch a 51% attack, meaning they could censor transactions. This is an existential threat to the network, but many developers have proposed countermeasures such as a POW change in the event such a thing ever happens.