all your assets. not just the ones you take with you

The US Exit Tax, or Expatriation Tax, is levied on individuals renouncing their US citizenship or green card. Governed by IRC Section 877A, this tax is specifically designed for high-net-worth individuals. It ensures that their worldwide income and assets are taxed prior to exiting the US tax system.

EDIT: the statute is at https://www.law.cornell.edu/uscode/text/26/877A