Imagine that some respectable country would go far beyond legalizing cryptocurrency and start one of its own. It would surely be no scam and it would probably have a strong support, but would there be any drawbacks to the currency and the state itself? Would it get more attention than some of the biggest coins now?
Imagine if a state announced it would enter the search engine business to compete with google. Or if the united states federal government proposed plans to enter the electric car market to compete with Tesla and Elon Musk. I think the response to those plans are what most would expect from a government entering the crypto currency world.
The main issue with many state run programs is they lack incentives to be efficient or cost effective in a way which would make them competitive against private sector entities. The state has a lot of clout but there are no metrics in place which would allow a person to determine how effective or ineffective tax revenues are being spent. Politicians tend to be entirely computer illiterate, economics illiterate, war and defense illiterate. They're often entirely at the mercy of analysts, campaign contributors, special interests or advisors as they themselves do not comprehend issues like net neutrality.
Part of the reason for bitcoin's success could involve people losing faith and confidence in governments to solve problems. In the USA the government has spent trilions attempting to fix issues like healthcare with little or no success. If the government released a crypto currency, there wouldn't necessarily be any real support for it. Not when the USA and european union are trillions in debt and not giving much indication that they are capable of successfully running things without destroying economies of their own country(if that makes sense).