A nation’s digital currency would still suffer from the threat of inflated supply, whenever politically expedient.

Also, most countries don’t want to use their own currency as reserve because they don’t have scale globally.

And they would prefer not to be beholden to giants like the US or Europe where they may have little sway and are vulnerable to financial system coercion - standard foreign policy for the US.

Bitcoin does not suffer (or suffers less) from those problems.