What you've written is accurate, but isn't relevant to the prior discussion.
I mentioned that printing money makes the US dollar less attractive.
Of course, others are also printing money (to a lesser or greater degree), so their currencies are also becoming less attractive.
But this is a short-term viewpoint, and the prior context was some point in the far future, when the Chinese economy is 2-3x the size of the USA.
Remember that:
1. the the US dollar is regarded as the reserve currency
2. the US has a persistent and large trade deficit
3. the US has a significantly negative "international investment position" - where it owes the rest of the world more in terms of financial liabilities
4. the US has a persistent and large federal spending deficit
5. There is a large and growing federal debt
So if the US government continues to print money, and run large government and trade deficits, eventually everyone will see that the debts and payments will be unsustainable. That would be the US Dollar losing the trust of the market.
So you don't actually need a significant crisis or alternative to emerge, as you put it.
The US just has to continue running large trade deficits which continue to increase how much the USA owes to the rest of the world.
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The Eurozone and China are also economic blocs that already rival the USA in terms of size.
But the difference is that both these currency areas have small trade surpluses.
That means they do not rely on foreign currency inflows to fund their government spending deficits.
Why does the us need foreign currency inflows for funding deficit? The US gov spends and taxes in USD. If there is a deficit, they can print more USD to finance that deficit. Sure if the deficits gets big enough and too much USD gets printed, hypothetically there will be inflation. But in reality, most of the USD printed ends up in the top 0.5% richest population who don't really spend that money on goods or service so inflation is subdued. Instead that money gets channeled to the stock market inflating asset prices. Which is exactly what is happening right now with the multiple trillion dollar printing operation and soaring stock market and near zero inflation.
My point being, as long as USD remains king. No country will unsurp US dominance. The only way to devalue USD is for some black Swan event to happen internally in the US.