OP-ED: "A Threat in Every Port," by Lawrence M. Wein, New York Times, 15 June 2009.
Great chart lists "132 ways to bring a bomb to America."
None of them involve a missile fired by a foreign state that would be immediately subject to retaliation.
I would give all that DoD missile defense money to Homeland Security's Domestic Nuclear Detection Office. I am certain that office could not possibly manage a more wasteful spending of the same billions.
Plus, we wouldn't end up pissing off other countries or erecting 21st-century Maginot Lines in Eastern Europe or Alaska ("Look, I can see a Russian!").