Security forces are soon to be equipted with Cyber 3 radiation detectors that will find with ease the smallest amount of radioactive material. You can't hide this stuff without tons of concrete and lead. More scare talk from the control freaks that want only to eliminate freedom. They never can stoop low enough.
However i do agree the greatest threat is probably a radiological dispersal device, not an actual nuke. However such a device would have far reaching ramifications that touched everything from the economy to social decorum. Imagine for example what would happen tot he US economy if one of those devices exploded in WallStreet?
Anyway i also share your views that many freedoms are threatened. And i believe that the moment what makes America America is taken away then the terrorists win, and there is a risk that some over-zealous congress meet might implement laws that curtail freedoms. And that is wrong because it would destroy the spirit of America, which is partly composed of the great freedom inherent in this nation. The US without rights and freedom is no longer the US, just the semblance.
Thus what needs to happen is a union between getting these crazies before they act, and the continual dedication to the great freedoms and rights in this country. Having safety without liberty; and having liberty without safety are both the same. Flawed! What is needed is safety with liberty.
Without safety the liberties of the US are at risk since the lives of Americans is at risk. However without liberty life in the US would be like life in most other nations in the world...... repressed suppressed and oppressed! And if you look at it all over the globe people die for freedom, people suffer for it,and risk all for it. People like Lech Walessa in 80's Poland, people like Mandella during the times of Apartheid S.Africa, people like Ghandi in colonial India. People of all creeds and colors, fighting to have a semblance of what the United States of America has. And as someone who was born and raised outside your borders i can tell you this, loose your freedom and you will discover why so many envy and hold you in praise (and why others hate you).... due to your great and mighty freedoms. And it shocks me when some act like these freedoms are for naught, and thus can be 'switched' on and off.
America is liberty.
Having a nuclear bomb takes more than a sack full of U-235 and plutonium.
Also, as you pointed out, radiation is the easiest thing in the world to detect.....remotely. Radiation detectors placed along the road could readily sniff it out.