Still, it will be an interesting question if IRS gets curious and there is no documentation stating that the Angola taxing authority actually received any of the withholding from your paycheck.
This has been my point in the past. I have no beef with companies withholding tax, if they are legally required to do so, plus they subsequently provide proof to the employee/sub-contractor that that withheld tax has indeed been paid to the relevant tax authorities. Proof may be some time coming as it could be 18 months after you actually worked on that particular contract. BUT if they cannot provide proof of payment the money should be re-embursed to the employee/sub-contractor not simply swallowed up into the company coffers.
It’s also up to the employee to request proof further down the line that the money was indeed paid out.