The first large-scale military use of EMP will not necessarily be against the US homeland. For example, Israel could use it against Iran. Such use would likely spur action elsewhere to harden electrical grid systems. In particular, it might serve as a wake up call in the US, where legislation to protect such infrastructure has stalled in the Senate.
EMP Blog
Preparing for an electromagnetic pulse event
this is exactly how i see things evolving, Israel sticks it to Iran to stop any further threat. However, lets hope they dont respond in kind to Israel and their closest allies. (the US mainly) Considering China has close ties with Iran as well… well lets hope things dont evolve to quickly.