Why do you think it is a prerequisite? Imperialism can certainly exist without having the reserve currency--consider the world situation on the outbreak of WWI, which was the height of imperialism and yet no country had a reserve currency (everyone being on the gold standard).
Taxes on USD are used to fund the military. I see long term value storage in Bitcoin with operational and privacy focused "cash" like crypto being pegged to BTC as a way to choke the input funds to the US military.
I'm saying it's much harder for the US government to collect taxes from crypto. It's much easier to work with a bank to directly pilfer your account than for them to force people to hand over their private keys. The latter doesn't scale nearly as well as the former.
