I'm not sure that Japan should be held up as an example of a...

I'm not sure that Japan should be held up as an example of a strong, stable economy...my understanding is that persistant budget deficits have been funded by it's citizens over the past 20 years, but this can't continue indefinately. Govnt debt as a % of GDP can't grow forever...when will it end? 300%, 400%, 1000%?

They have an ageing population who will not continue to invest in govnt bonds, rather they may become net sellers in order to fund retirement.

The US is in a different situation, the biggest holders of treasury bonds are the Fed and China, and US budget deficits have blown out exponentially over the past 10 years.