You just need to read The Confessions Of An Economic Hitman by John Perkins who worked for CIA/NSA through its associates i.e business covers.
Crude Oil is the currency of the world. And what is the currency of crude oil? Dollar! And which country has a monopoly or a license to print the dollar? Only one country i.e U.S. Members of OPEC HAVE to sell oil in dollar it is part of the membership agreement. Where countries have tried to use other currencies like Iraq there has been a regime change. Once the world stops selling oil in dollar the U.S cannot get a free ride from the world. Like other empires before it the US is also looting and exploiting the world but it is more subtle in its ways.
Only Russa and China are powerful enough to resist the US militarily and then have started a process which would take a lot of time to mature.
The US has a lot of reserves of oil and gas that it does not want to use because it can get it for free from elsewhere but it may need to start using its own oil if the world stops selling oil in dollar.