I would think the present course of countries selling Treasuries is a pretty good indicator - but it would take something else, like, say, disclosure that there is no gold in Ft. Knox might do the trick.
Japan is selling US Treasuries because the yen is closing in on 160 again - levels not seen in over 30 years. Their people are suffering.
They're selling US Treasuries and buying yen with result, in a failing effort to prop up their currency.
It's not because they hate the US.