Snowden's choice of helper countries is a national security risk to the United States. Here you have someone in possession of (still undisclosed) state secrets from his work at the NSA, and who needs help from a foreign government. That's the very definition of compromised. What is he going to trade for protection? More classified information, of course--possibly much more sensitive information than the existence of programs like PRISM, which foreign spy agencies have likely known about for years. He has national security information, foreign governments want it, and they eventually will get it. This intel will eventually flow to China and/or Russia, where it will remain secret and used against the United States.