Kennth Rogoff actually wrote a book called: this time it is different.
For USA and Europe COVID-19 has been really expensive whereas China in particular has grown through it. The US relies on Asia - in particular China and Japan to cover that cost by buying US treasuries in an slowly inflating currency. At the same time the relationship between China and the west is increasingly antagonistic. This creates a different dynamic from 2008 - how different - time will tell.
As of the end of 2020, there are 27.7 trillion dollars in outstanding public debt. 10.8 trillion is held by the Federal Reserve and the US government. About 7 trillion (no data since September) is held by foreign countries. Of those, China owns 1.07 trillion and Japan owns 1.29 trillion. I don't think it's reasonable to characterize the US as relying on China and Japan to cover those costs.
The other major (all holding > 100 billion) holders of US debt overseas, in order, are the UK, Ireland, Luxembourg, Brazil, Switzerland, Belgium, Taiwan, Hong Kong, the Caiman Islands, India, Singapore, Saudi Arabia, Korea, Canada, and France. This seems like a pretty good mix.
NB: Real yields on treasuries are all negative. People are buying treasuries despite knowing they will lose money in real terms. I don't think people giving the US free money just so they can hold t-bills is a sign of the weakness of the US dollar.
The numbers sound big but then in different perspective not so big. The internal debt of the US, in some sense, at least when we are thinking about the viability of the US dollar in international trade, cancels itself out. And debt and swaps with Europe or the UK? Perhaps it matters less than debt to other countries.
It really boils down to the exorbitant privelige. How big is it really? Who exactly bears the cost and who encurs the benefits? Not exactly clear in the details.
However were Japan and China to give up their "mercantalistic" practices of buying US treasuries and instead letting their own currencies appreciate and start trade and investing without using the USD.
For USA and Europe COVID-19 has been really expensive whereas China in particular has grown through it. The US relies on Asia - in particular China and Japan to cover that cost by buying US treasuries in an slowly inflating currency. At the same time the relationship between China and the west is increasingly antagonistic. This creates a different dynamic from 2008 - how different - time will tell.