Its power stems from sovereign, contiguous territory with resources, or a network of global treaties both economic and military.
In contrast, Britain was a globe-spanning empire, which disintegrated with national independence movements.
The equivalent would be if California and Texas decided to split from the United States.
And as the quip goes... the next few largest economies, including China, are pretty incentivized to keep the global economy rules as-is, because they benefit.
De-dollarization is happening, but is going to be a slow shift, with an uncertain outcome.
And I think in two hundred years when history is written by someone who is dispassionate about it, the US empire will be seen a continuation of the UK and Dutch empires that was before it.
The key difference with the post-WWII economic world order was that the US generally tried to ensure that everyone else got theirs.
Granted, the US got more, but there was insight that a global economy that benefited all was more stable than a system that left powerful economies outside, with an incentive to topple it.
Simplified empire is about ever increasing conquest and exploitation. At one point the conquests and military upkeep becomes more expensive than the spoils and the whole process starts going in reverse.
Of course I am not saying that this is what is happening right now; maybe Russia and China are falling apart and we are entering another unipolar moment.