> Can you name a safer financial instrument than US debt? Its definitely not fiat currency

I dunno. I mean, US government debt is conceptually subject to both US monetary risks (the same as US dollars) and US government fiscal risks, so US government (dollar-denominated) debt must always be (even if only infinitesimally) less safe than at least one fiat currency, to wit, the US dollar.

Depends on what risks you are looking for. Singapore debt might be in sounder management, but of course the country is smaller; so more of a playball.