First some background... VATs (value added taxes) are pretty solid for distributing this money fairly between the national entities involved in producing this wealth. Currently companies cheat the system a bit to do the bulk of their value adding in nationalities that don't tax it highly (the famous putting stickers on computers in bermuda in apple's case).
I think it is fair for a nationality to claim that there is a certain minimum amount of our production we wish to divert to social causes, in that case I also think it is fair that, for products sold in that nationality the government can claim any shortfall in paid taxes on the value accrued to that point. Let's assume that China has a 10% VAT on 5% of the value, Bermuda .5% on 90% of the value and USA 8% VAT on 5% of the value. The tax owed to the US might be calculated by ignoring the first 5% of the value, since china already collected a sum exceeding the sum the US would collect, then the US would collect a 7.5% remainder tax on the middle 90% and a full 8% on the last 5%.
These collections would only be owed on products sold or incrementally improved in the US, any items that never entered the US could live by their own rules.
Regarding the IRS taxing the wages of expats living abroad, it follows much the same system. An expat is only required to pay the difference between the taxes they are paying and the taxes they would owe if they resided in the US, this is a silly rule that probably shouldn't be on the books since expats living abroad gain none of the benefits from their citizenship.