Now that I read the quotation more closely, though, I find cause in it to reconsider my original opinion:

> [...] in a manner reasonably calculated to convey the impression that such use is approved, endorsed, or authorized by the National Security Agency.

Frivolous as I find it, I rather strongly doubt that anyone is going to mistake McCall's parody for something 'approved, endorsed, or authorized' by NSA. As such, I doubt the case will get anywhere near the Supreme Court, unless whoever in NSA's legal office is behind the C&D really feels the need to pursue a hopeless cause that far; it seems almost certain that the first court to rule on the matter will do so in McCall's favor.