Instead, figure out (or estimate) what percentage of the shares are owned by US residents. Multiply that percentage times the corporation's profit times the corporate tax rate and that is what they should pay.
Note: Any public corporation knows who are the immediate owners, so that they can send out shareholder info. However, a shareholder might be another corporation which is owned by other corporations, etc. Hence, the need to estimate (along with following the money as much as possible).