A direct strike on a west coast city might kill tens of thousands.
A detonation well above the west coast would send an EMP pulse that would put a significant portion of the west back into the pre-electronics era, the resulting devastation to our society would cost us millions of people in the first few months after.
I had the EMP discussion with an electrical engineer just 2 days ago. In a nutshell, a deliberate EMP is a very difficult feat to execute. At most an EMP would disable circuit controllers on transmission voltage lines, which have manual operated overrides and could be back in operation in hours. Modern circuitry would likely be unaffected. Radio transmitters would be susceptible to damage. Again, this comes from an engineer. I claim no knowledge or experience with EMPs.
Please correct me if this is wrong.