USD is supposed to be a bubble, because that's how it was designed (at least after Breton Woods). I realized this when trying to figure out when the GDP of China would be higher than the US, and seeing that this depends less on real Chinese production and more on the crazy valuation of USD.

A lot of US economy is not real. A lot of the GDP is based on financial services, real estate, and stocks (including tech), which are pure bubble money. A lot of the economy is also based on health care, which basically doesn't exist is a decent country with public services. The other part is "defense", which means they threat the rest of the world into growing their economy.