[danenania]

The US already claims tax dominion (for its citizens) over the whole world. You get the foreign earned income exclusion, and you can also avoid double taxation in many countries that have a tax treaty with the US, but otherwise the default is that you need to report and pay income tax on worldwide income, no matter the source and no matter where you are a resident.

In the same vein, if the US were to implement a wealth tax, the simplest way in terms of enforcement and not creating perverse incentives to shelter wealth outside the country would be to make it international in scope. Yes, people could give up their citizenship, but that's a huge sacrifice which most wealthy people would not want to make at any price, and there's already an exit tax in place for people that do this.