Virtually ANY country can build or buy an EMP weapon. Imagine something along the lines of New Orleans without the flooding, but worse. No telecommunications services, cellular or landline. Water and power stations kaput. No water, no electricity, no gas, no cash withdrawls, no credit card use, no automobiles, no traffic lights, no nada. Virtually everything that operates on electricity ceases to function, except for flashlights and cordless drills(not an all-inclusive list). It wouldn't be too long until vital resources get used up. Even hospitals would go dark.
It isn't just China that could use this technology, it could be Sierra Leone for all we know.
I think the US gov't should develop a new test site for an EMP bomb. Patterson, NY sounds like a good place as any.