Which specific aspect of this package constitutes an "unlawful circumvention device"? If the Snaphax class instantiated a different low-level class from SnaphaxApi, that was written to a slightly different API, would it still circumvent? If so, why must the entire package be taken down? If the code here was used but pointed at a proxy, would the distribution of code itself still have limited commercial purpose and be designed or produced primarily for the purpose of circumvention? The actual USC section (Schaffer has the wrong subsub: it's (a)(2) (and maybe (b)(1)) not (a)(1) that governs "traffic in any... device") refers extensively to copyrighted works: what copyrighted works are referenced here? Do Snapchat claim copyright in their users' images? If not, what do they mean here?

Without specific answers to many of the foregoing questions, this message amounts to asking OP to forego all use and value of work that OP has personally performed, merely on Snapchat's say-so. So, actual meritorious C&D's require some actual work on the part of the sender. This letter took some knucklehead five minutes, so that's about what it's worth.

C&D's are usually courtesies to avoid...

...the expense of an actual lawsuit. In many cases a vague and overbroad (see above) message is mere bullying, attempting to imply threats that would be impossible to articulate or enforce. Papers filed in a court are held to a higher standard, and penalties are enforced. The fact that OP might be well-advised to retain counsel in response to this turd is an indictment of the USA legal system.