The first casualty of war is said to be truth, and a close second is civil liberty. As we necessarily become more alert to terrorist threats, we should be just as vigilant of our own liberties as Americans. If the defense against terrorism makes us a police state, terror will have won.
America is now a different country. But even in a world where every American is a potential target, it's possible to have higher levels of security without sacrificing basic liberty.
Europe takes airport security far more seriously than we do, but still maintains functioning democracies. Even Israel's state airline, El Al, keeps its planes flying safely, with meticulous inspections, armed guards, and anti-terror training.