tax base is global - that is only the case for the US, which is why the American Tax Payers are not the only people funding the US Government. Remove the US ability to tax abroad -
- and it will be the case that the US tax payers in US itself becomes the only creators of tax revenue.
Mostly companies and industry that is based in the US but operates abroad, the companies of course use every method in the book to reduce and delay tax payments, but they folow the law
Only the US, The US has about the same GDP as all the other G7 nations combined, and they project superior militarily power over all international water and is an invaluable market.