This is an interesting question but I think you have misinterpreted what these countries are doing. They are planning on adopting blockchain technology to track their own fiat currencies, not a decentralized crypto like BTC, ETH or LTC.

For example, the US will never accept BitCoin for payment of taxes. All income calculations within the US for tax purposes will be calculated in USD and not an alternative, otherwise there is no way to apply incentives/disincentives through the tax system.

One of the real values of fiat is that you can be guaranteed to pay your taxes or employees with it.

Like @inegoveritas says, they may create an equivalent currency that operates via blockchain to increase tracking and collection but they will not adopt one of the currently circulating coins.