How can they reverse/ delete a transaction? There is no such thing as editable blockchain! Basic 101
It 's possible and can happen in Bitcoin; you need to have access to the longest series/chain "The longest chain is always reliable/trusted So the blocks from all the mines could not work against you."
So a 51% attack can reverse a transaction.
If the government issues its currency, all the nodes under its control & will always have trust under its control.
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Need an explanation over 51% attack. How strong is Bitcoin against 51% attack! If government agree to open a blockchain, it would be a new beginning for Bitcoin step up to new height and growth. With government intervention, we secure more about transactions and avoid risk from hackers.
I do not think the government's use of cryptos will end the danger of hacking, as the hackers can still hack markets and others, but they will have a safe payment.