There is a difference between a declaration of martial law and a draconian crackdown...

I would like to challenge everyone to examine more closely what martial law actually is, and then... consider what has effectively been declared with the National Defense Authorization Act of 2012 -- especially when taken together with previous legislation like the Patriot Act.  I won't condescend to explain here what the NDAA or the Patriot Act is (follow the links), but I'd really like people to take a moment for consideration about the implications of this growing body of overtly authoritarian, and even totalitarian, legislation.  While most cities and towns don't have tanks rolling through their streets every day, and while curfews are rare, I'd suggest that there are more subtle factors to martial law than these things.  Additionally, while a widespread crackdown and purge of assorted "radicals" hasn't occurred yet, I'd like to point out that the legislation in question allows, and paves the way, for precisely that.  This legislation is, effectively, a declaration of Martial law by the U.S. government.  While arguably few people have been subjected to the worst effects of this legislation, the declaration has been made and many people are, basically and technically, existing in violation of current U.S. law.  If you are living within the borders of the United States of America, you are living under martial law at this very moment. 

Finally, while I don't want to argue too much about definitions... the U.S. has more prisoners per capita (and in total numbers) than any other nation on Earth.  Wiretapping and other broad surveillance measures have been codified by the state.  American citizens can now be arrested by the military, detained, and imprisoned indefinitely without the right to a trial.  All of this amounts to the very definition of a totalitarian police state.