There are lots of ways… you could back it with a basket of real assets (eg gold, commodities, etc) or multiple currencies (eg to reduce the role any one central bank plays) or create a new process for delegating central bank authority (eg with better transparency). I’m not saying I have the answer but I’m quite confident that in the next few hundred years we will have digital and stable mediums of exchange that are better than the US dollar for most holders, in terms of lower inflation, more interoperable, more transparent, more stable, etc.