Actually there was such a system in place. Well, a similar one, at least. It's called "Visas".
Many of the terrorists were apparently here on lapsed Visas (and had known terrorist links to boot). Why weren't they rounded up and sent home then? You tell me.
If the FBI doesn't have the political willpower to round up and send home people who are known to have terrorist links and lapsed Visas, then what makes you think they will after a Nat'l ID card is in place?
Could it be because the Toon had sent the CIA instead to find those evil video pirates instead of dangerous terrorists at the request of his Hollywood buddies?
Nah.
GREAT question. Good clear thinking. What will change? In fact, our FBI, CIA had all the evidence .... and did NOthing. Our Government has FAILED us.