I understand that prior to crossing being admitted to the US the rights I take for granted on US soil do not apply to me. But it isn't clear to me when passing through a US airport where "admission" has occured. Unlike, for example, the UK, where clear signage unambiguously marks an actual border, US airports have a confusing series of stages to pass through.
At what point in passing through these stages have I technically been admitted to the US, and acquired the full legal protections I expect there?
