Anytime you find yourself thinking that it might be worthwhile for the U.S. of A. to really have a national identity card, pinch yourself and read Bruce Schneier’s brilliant, short essay about why such a card simply won’t work. Here’s an excerpt to whet your appetite:
“Currently about 20 percent of all identity documents are lost per year. An entirely separate security system would have to be developed for people who lost their card, a system that itself is capable of abuse.”
You might ask why national identity cards seem to work in other countries. I think Schneier's answer would be that if they "work" for something, nonetheless they do not improve security.