I'll respond today or tomorrow to comments on this. Today, I just want to emphasize something.
What if you're a CITIZEN of the US not carrying papers identifying yourself as such? You can ALSO be stopped and PUT IN JAIL. You probably will assume this won't happen to you if you are blond, but don't be so sure if you are not.
And what if you just happen to be annoying to someone..they don't like what you're wearing or saying or the way you're walking or that you're a teenager. They can claim they suspect you're not a citizen.
The US is NOT supposed to require that people carry ID proving they are citizens!
This is not just anti-immigrant, it is clearly racial profiling of the worst sort.