"If you're within 100 miles of the border and you don't have a passport or other proof of US citizenship, you get detained."
No way!
I live within 100 miles of the border and that would mean I would have to carry a passport anytime I left the house!
Let me finish the thought, "A valid driver's license would be other proof of citizenship." Of course, that would require that we don't hand out licenses to anybody that just walks in to the DMV.