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.
It's the same situation in most countries around the world, forced by global circumstances and changes to use the dollar in exchange for American protection. World War II contributed to the rise of the dollar, followed by the collapse of the Soviet Union, which strengthened the dollar's position despite all its crises. The global economy finds itself entangled in the use of the dollar and unable to abandon it. As long as commodities in global trade (gold, oil, other minerals, etc.) are priced in dollars, no country can escape American hegemony unless it isolates itself from the global economy.