Good idea, I think the Salesforce tower in SF cost $1-2B.

Are there any countries for sale other than the USA?

Because the asset price would crash if they tried to cash it. One is simply it would crash from the supply of that asset, but also it reflects to the broader public that the asset holder values cash higher going forward than the other asset which means that others would use that signal to value cash higher as well leading to a snowball effect.