Radiation isn't some sort of dust. Its a bunch of highly energized particles that can pass almost through any material, the more dangerous alpha waves are going to be the ones closest to an explosion or radiation source, every thing else can be protected by staying indoors and near solid objects, Any radiation blown over here would be protected against by staying inside. Now the issues with contamination are a whole different story, You would have to worry about plants, water, animals, etc. For example Chernobyl and Pripyat have completely demolished parts of forest and buried a lot of land under 6 feet of dirt to keep all the radiated shit underground. A lot of the area surrounding the sites have gotten better in terms of radiation. Now in the case of the US we won't be exposed to nearly as much radiation as Chernobyl and Pripyat, but at the same time any abnormal amount of radiation is something I would want to avoid anyways. So is it something we need to worry about? Yes. Will it wipe out the west cost? Probably not.