How does a country fully adopt Bitcoin?
First, they should get a mentally deranged government.
This is easy. All western government are mentally deranged (someone more, someone less).
Icenlandic Kronur are around 14400 ISK/BTC today
Seriously?
0) Acquire 100K BTC (today) or better 200K BTC.
1) Legalize the circulation of BTC along the official currency. (no profit taxes on gain from increase of BTC value, legal tender laws, etc.)
2) Announce the will of the government to switch from fiat to BTC in a number of
years months.
Fireworks ensues.
People will pay their taxes in fiat (because of legal tender laws the government must take the currency) and the government will use that fiat to pay back the central bank loans (making the currency unit disappear as they cancel the debts) and pay government employees.
Government employees will convert their fiat to BTC ASAP (and at a discount) and the fiat will be used to pay taxes by the rest of the population.
This should allow to drain the fiat until it will disappear completely from circulation and people MUST pay their taxes in BTC because they have no access to fiat (at a discount).
There could be a "little problem" on this plan: there is near always more debt in fiat than fiat in circulation. So as fiat and debt cancel each other, the value of fiat will increase faster than the value of BTC, because there will be left a debt to be repaid with fiat that can not be repaid in fiat because there is no fiat left.
So, the government must evaluate how much is the difference between central bank issued debts and fiat circulating and decide the conversion rate in BTC.
So, if there are 100 B ISK circulating and the central bank have 200 B Kronas of total government assets and liabilities for 400 B kronas, the government could decide to put a max exchange rate of 1M ISK/BTC (10K US$/BTC)
This should cover the 100 B kronur difference in their balance sheet (so the central bank will not go broken when no one is able to pay back the debts in kronars).
A nice discount (10-50%) if people pay their taxes in advance or in BTC or double discount if they pay them in advance and in BTC.
Substituting the Monetary base of Iceland (100 B Kronurs) with BTC would imply, at minimum, 40$/BTC (if all 21 M BTC were used just by Icelanders). It is 100 B ISK/21 M BTC --> 5.000 ISK/BTC.
If they want do it, they have not so much time to do it.