>>That could be done at a national level, and perhaps individual states could retain the right to track (or not track) ballots systematically as they see fit, as is now done in the current state-by-state system.
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>I think not. I've now checked the constitutions of 25 states. 19 of them have secrecy guarantees. For 5, I couldn't find anything definitive and 1 (Texas) specifically requires traceability.

How else would you handle it other than to leave each state able to retain their own current method? All I'm suggesting is basic states' rights: Those that have secrecy laws can keep them, those that don't won't be forced to start applying them.