The Empire's key anchor to power lies with its cozy association with the Medieval-like kingdoms of the oil-rich Middle East. Major components of this association consists of their commitment to sell oil only in US dollars in exchange for Empire protection (see this, and this) which insured the value of the US dollar, and their huge purchases of weapons from the US insures that their oil revenues get recycled back to the US's military-industrial complex.
...billions of dollars from Arab oil exports began to flow back in exchange for new American and Western-made weapons arsenals. According to rough estimates, in the next few years, the Arab Gulf countries will buy weapons worth over $ 120 billion. American arms dealers are again rubbing their hands together and counting the windfall from their bloody business.