How would you prevent billionaires from moving to a tax haven, though? That is the big loophole that both billionaires and large corporations benefit from, that others don't have access to.
A country as large as the US has plentiful ways to ensure tax compliance by citizens. It's small countries that are forced to remain competitive. People won't flee the US by the millions just because you raise taxes.
For example you can calculate how many percent of their revenue a company made in a given country and then how much tax they paid there and demand them to pay the difference.
