I agree, tell them what they want to hear. They want to hear that you will move to HKG in a heartbeat if you had to. They will also tell you that you could spend your entire career in the US and they are correct. However, they still want to hear that you are open and willing to go wherever.

Also, it may be an FO interview but they may ask if you would be willing to be an SO if offered. The answer is "absolutely, I just want to get in with a great company". This is a test ladies and gentlemen, if they want you for an FO slot they will offer it. If they offer you SO then you can make the choice. Cathay doesn't hire to fill classes in two weeks so if you went in for FO and got offered SO, it isn't because they just needed SOs that day. It is most likely that they liked you but something went wrong in your interview or sim. You answering your willingness to be an SO lets them know that you just want to get in to the company. If it is a career stop, may as well get on the seniority list. If you were to answer no to the SO question, chances are you would get a thanks but no thanks instead of the SO offer.