An EMP is actually an interesting point. Makes me consider a lead casing for one of my wallet file backups. However, counterfeit BTCs or any sense of wiping out ALL BTCs is highly unlikely. An EMP targeted at one specific location would disrupt the mining network and potentially destroy some people's wallet files but in no way could destroy every single BTC or stop the peers in the network from continuing.
It makes me wonder, what happens to the BTC infrastructure if, say, a country is completely cut off from the outside internet? For example, Egypt during the Arab Spring? If there were enough peers inside that country would they come to a consensus about a particular block and continue the blockchain forked from the rest of the world? Or would the peers in the country not be able to "access their funds" because all transactions would be unconfirmed?