According to this report, President Trump is ready to bomb North Korea's nuclear sites:
Take a look at this simulation of the North Pacific jet stream:
It will take any nuclear fallout across the Pacific all the way to the US West Coast.
Smooth move, Ex-Lax. You may get the North Koreans, but you'll also dose your own people. I don't think very many of us signed up for that.
The fallout also may hit South Korea and Japan, but not Russia or China.