bitcoins cannot be frozen or seized by any government or private actor
This is categorically untrue in the United States. What do the following mean?
To coin Money, regulate the Value thereof, and of foreign Coin, and fix the
Standard of Weights and Measures;
To provide for the Punishment of counterfeiting the Securities and current Coin
of the United States
Those are powers specifically granted to COngress by our Constitution. Your bitcoins could be declared worthless foreign coins, exchange rate of zero, at any point in time by Congress. Possession could be made a crime just like possession of child pornography. Those are hardly characteristics that excel traditional currencies.