The whole December 2012 thing coincides with the transit of Venus, aka the Mayans God (Venus).
The Solstice on December 21, 2012 at precisely 11:11 AM Universal Time marks the completion of the 5,125 year Great Cycle of the Ancient Maya Long Count Calendar. Rather than being a linear end-point, this cycle that is closing is naturally followed by the start of a new cycle.
2012 is also considered the completion of the 26,000 year Precession of the Equinoxes cycle, and some say it also signifies the end of a 104,000 year cycle.
Supposedly a polar shift occurs every 26,000 years, and NASA isn't sure if it happens quickly or slowly. NASA also aren't sure if the polar shift causes a change in the rotation of Earth. The thing is, regardless of the shift occuring quickly or slowly, the rotation direction would have to change slowly because there is way too much mass and kinetic energy, to the Earth's rotating iron core for Earth to just spontaneously reverse it's rotation.
Now if rotation change occured slowly it would mean a long draw out period of nearly no rotation or very little rotation. Do some research on the earth's rotation and gravity, and you will see that it would absolutely destroy the planet beyond belief.
If rotation change occured abruptly it would send the oceans toppling over continents, and obliterating tectonic plates on a grand scale, and on such a large scale you'de have massive extinctions every 26,000 years. Whether rotation change occured slowly or quickly you'de see massive extinctions in the fossil record every 26,000 years, which is not the case.
Even if a rotation change does occur and happens slowly, without completely destroying the world, water would gradually be readjusted around the world and lots of places will be flooded, but as a whole the USA will be fine other than losing some major cities... a problem yes... apocalyptic... no.
And lastly there is a supposed "planet x" which I'm skeptical of, but can cause flooding problems (if it exists) if it passes behind the sun when making it's apex orbit around the Earth. This still wouldn't be apocalyptic... it would just flood major cities at most, that's if it does anything at all.
Any way you look at it there are flaws to all the presumptions regarding 2012.
The whole 2012 thing is blown out of proportion if you ask me. It's just the ending of a cycle or calander. Not to mention the whole 12/21/12 - 11:11 timing is a little too "corny" if that's the right word. That date/time is all 1's & 2's... those numbers coinciding with an apocalypse are something out of a movie if you ask me.
PS - sorry for the rant ahead of time.