I believe that it is VERY difficult for any EU country to accept a BTC reserve or other cryptos
The economic protectionism there is big, in addition to having to go through the government of the country itself, it still has to go through the EU, and we all know how difficult it is for something innovative to be accepted there, there's IMF too
I think it's much easier for Asian countries like Japan, China and South Korea to make a reserve than European countries, or even some African countries