means, the biggest bitcoin holder is US government?
No, Satoshi Nakamoto remains the largest bitcoin holder, holding over a million. And of the states, the small European country of Bulgaria has 213,519 bitcoins, so from what we know from open sources, it has the most bitcoins after Satoshi Nakamoto.

We never know if Satoshi will be back or not. He might not be back! Even if he is alive, he might not move it for a long time and his address will remain dormant. BTW, I didn't know about Bulgaris's holding.
That's right, we don't know. But that's the beauty of bitcoin, that our knowledge doesn't matter. Satoshi Nakamoto remains the owner of his bitcoins whether he wants to spend them or not, whether he is alive or not, whether we want him to spend them or not. He has full control over his bitcoins. And no state or organization or anyone else has the ability to influence this. Only theoretically the entire Bitcoin community, but it will not do this.
