All the tricks were already invented during this century. The taxes to the rich guys, at the end, will only affect those in the middle class with medium-high salaries (do you recognize here my friends?).
Well, you don't have to actually store your wealth where the island state can get to it. Just because you're resident in the Cayman Islands for tax purposes, doesn't mean you need to hold your wealth as Cayman Islands Dollars, or store it in a Cayman Islands bank.
Banks in Switzerland and London are more than happy to look after your money for you, denominated in whatever currency you choose.
Additionally, there is an exit tax which captures unrealized gains upon renunciation.
So, yes, American citizens are a small percentage, but if the USA adopted wealth taxes, it would have an outsized global impact.
Who really gets screwed by this, are middle class people with children!
The classic middle class trap: the working class are subsidised by taxes; the rich can pay enough to avoid taxes, and the middle class pay taxes.