It's not the interest rating of the US$ which makes the US Currency so popular. It's the falling currencies of the nations not living under Euro or Dollar domains.
Do you think that this is one of the reasons why countries wish to be independent from the US dollar? We don't live under Euro and Dollar domains and our currency is getting weaker but despite everything, people want to be near to US and EU as much as possible. It's a little bit strange but my country tries to become more dependent on US and Euro instead of getting rid of it. The reason why we want this is that US and EU countries are rich. After the fall of the soviet union, lots of people migrated to the EU and the US. They managed to build a better life in these countries and they also managed to send money to our country to help their mothers, fathers and relatives. Because of this, our country sticks with the US dollar and I feel sometimes shocked when other countries try to get rid of the dollar or Euro and join BRICS.