Once you clear immigration and customs are fully within the US, you have the same rights at the TSA CP as do we. However, some TSO's may not view it that way and may use their position and your lack of US citizenship to exert authority they do not have. If you question some action as being out of bounds, it is fully within your rights to request a supervisor for clarification before proceeding. Done politely and sincerely will help, at least most of the time. Asking for the TSM, the FSD or an LEO will get their attention as most people without knowledge do not use the acronyms. People with knowledge are more dangerous.