swh
Whether or not he was originally employed in HK or not isn't relevant. My understanding is that he was US based, he starts and finishes work there and that is all that matters. Same reason why CX had to back pay the Aust. based crew for LSL.
Regards the IRS and foreign banks they are being strong armed and forced to do so by US courts as they have ops in the US and their US based subs will be penalised if they do not comply. If you didn't have any presence in the US you could tell the IRS and the US courts to go and get stuffed. US requirement to pay tax on world wide income is a US IRS problem and not a problem for anyone else unless you physically do business in the US.