What is the absolute worst case scenario in regards to Japan, regarding US?

Question:

What I'm asking is, what is the absolute worst thing that could happen to the US, regarding Japan's nuclear disaster? Would it blanket America?
End the world?
Kill off nearly every living creature on Earth?
What is the worst case scenario, the absolute worst thing that could happen, and it's effects on the rest of the world, not JUST Japan?

Answer:

The worst case scenario is that a bunch of people like you will be freaked out about nothing and cause yourself a bunch of unnecessary stress. This stress will increase your blood pressure, cause ulcers, and lead to an increase in drinking, poor diet, and worsening health. This stress will not be caused by an actual health threat, but by your own ignorance and refusal to learn about the basics of chemistry, physics, and biology. Oh, right, I almost forgot. It is likely that a bunch of similarly ignorant women will abort perfectly healthy babies because they are afraid that some trace amount of radiation will affect their baby. (Thousands of women in Europe did this in 1986 after the Chernobyl accident.) So, all those abortions will be a VERY BAD THING. But, any actual health threat? Nah, nothing gonna happen to the U.S.