Um, yes they can, and they do.
CX/HK already capitulated to the US government on the cargo price fixing fines, or the money laundering fines imposed on HSBC.
HK companies don't have to co-operate, but having the US government shut down not only your US operations, but also any part of your business that might impact the US, is a very effective way of getting "voluntary" co-operation. Plus the threat of jail time.
Is it a legal shakedown? Yep, absolutely. Ask Iran how effective fighting it is...