on my opinion, blockchain technology can damage the country (on some time)... most of countries have centralised system and its too hard to change it on 100%, so... anyway - decentralised system is cool and it have right to exist in our lives
There some country using blockchain technology because it has the fastest transaction compared to any online transactions.
One thing that government refusing bitcoin or other currencies because it is decentralized and there's nothing to do with manipulated these cryptos. So, some of them decided to ban due to avoid near in the future that bitcoin may compete with the bank near in the future, and those maybe ruin in most countries.