Chilling words.
YOUR PAPERS PLEASE!
I don't normally carry proof of my US Citizenship on me when I am out and about. I guess that I ought to carry my US Passport from now on, since other than my driver's licence and my retired Military ID, the only other thing that comes close to showing citizenship in my wallet is my Canadian certificate of citizenship (dual citizen).
Who knows, I might, if your wish comes true, find myself on a bus up north some day for not having the proper papers on me.
(Don't get me wrong, as a New Mexican, I fully understand the problems of illegal immigration. However, I am not so sure that the rest of us need to carry proof of US citizenship on us at all times to solve the problem.)