I have not learned about Ripple, but I see in market vip indonesia Ripple is still affected by up and down Bitcoin, that means Ripple is also not an independent coin
If the government wants a coin that they can control, the government can use steem by signing up into a witness steem, so every country listed as a witness steem they can control it together
But if there is only one single currency in the world, it also will not be good because there is no market competition, it's all just my personal thoughts