Sounds a bit rash. A lot of index funds "balanced against the world" but 50-75% of their fund allotment into the US. This'll have to change and another country will have to rise up but this country will have to attract investors (eg not have an authoritarian or considered authoritarian government). There aren't many countries in that have some sort of democratic system that are normally more trusted by investors.
Bitcoin
Not many countries trust bitcoin. Although bitcoin is trusted by investors, it does not mean that the government will accept Bitcoin as a form of asset that can replace gold or USD. Dollar has been involved in our world for many years and it is not easy to take them down. Moreover, I love the dollar somehow. And as you can see, the bitcoin price is currently related to the dollar.
Therefore, in my opinion, it must take decades for decentralization to replace the dollar. And, I think that both dollar and bitcoin can be a part of our world. They will corporate and boost our economy even further. The replacement does not always bring advantages.