The United States is now far from that, and the eurozone has a growing "shifting potential", economically speaking. It is also in my opinion that no instituted government would adopt the currency; only people could. People who live in a country.
Right. And legal tender is a government edict stating that the currency, when offered as payment for debt,
must be accepted. So, nowhere will ever do that.
Now, an accepted currency? That's possible. It might even go so far as to be accepted by a government in payment for fees and taxes. I doubt it, but it might. But unless it is actually made illegal, sooner or later some region is likely to become a place where you can live entirely (or at least, almost entirely) in bitcoin. I'm betting on Nevada or New Hampshire as the first, myself.