Not sure what you mean by NSA. The C2 or the executive (not described how here) can reject a bill, if the majority, perhaps 60% of the C2 have a secondary vote, then it can go to a broad referendum for all citizens to consider.

The NSA effectively control the cyberspace of the US and therefore can make your electronic election to have any result it wants to. The Chaos Computer Club and associated people have fought voting machine for quite some time now because they effectively mean that powerful people can easily rig elections.