US entered decline after 911 British only stopped training the yanks on how to run a fleet during the 80s
They were a economic super power from the 40s mainly due to their lend lease program which gutted the wealth of the British Empire and overseas territories -> sending gold, and broke the back of Britain by being one of the few countries to actually repay it after financing Germany's rebuild (think we repaid WW1 just a few years ago).
Also the US push for the breaking of empires alongside our completely leveraged position fighting for Europe and freedom (remember the yanks only arrived towards the end, the Russians would have arrived slightly later but otherwise it would still have been won).
From the 80s when the US could finally field a fleet without training conductors onboard that's when they become a world super power - Saudi has all the tools for example but none of the knowhow on how to operate without US trainers or mercenaries from the private military services) that was basically the US up until that point and with the absorbing of the brightest minds from Germany and theft of British, French atomic knowledge (and then shutting them out) the US was well placed to become a world leader.
But 9/11 changed everything - they over extended themselves and have continuously done so since.
They can of-course reprice the gold in their vaults to modern values to extinguish their debts but the world would be very volatile during that period.
The dollar isn't itself the world reserve currency, the demand for $ to service the Euro dollar market which is the world reserve currency (ledgers) is 400 trillion in value of offbook and on book debts that's the only thing really keeping the $ alive internationally, the oil demand for dollars is the basics of its velocity but is tiny in the world of trade so when you begin to see debts being created in higher velocity then you know the dollar will end and the US will then start to implode.
For now it's like a supernova sucking everything in and up.
