Police officer: I suspect you are not an adult, show me your ID!
is that correct and are you forced to show it then? Or just be arrested on the spot.
It comes down to a presumption of innocence that's intrinsic to our way of life. If an officer suspects I'm not an adult, he needs to have reasonable, articulable cause (RAS) to detain me. He'll have to convince a court of that. A "hunch" is not enough.
We have a unique system of government in which our Bill of Rights reserves certain rights to the citizenry, and the government must prove a significant burden of proof or necessity to infringe upon them. Among those are protection against unreasonable search and seizure, and against self-incrimination.
Most European countries have documents that make vague promises to respect vaguely-defined rights, but they are not as specific or as stern as our constitution.