It turns out, if you want a pre-created list of US tax codes which can be imported to Magento, you either need to pay for it or create it yourself.

Based on the file shared by Richard Ricketts, I searched for the official, most up-to-date state sales tax percentages, which can also be found on the Tax Foundation's website.

Instead of charging for it and to follow in Richard's footsteps, I'm offering the file for free, to the public domain.

You can download the US per-state tax codes in a CSV, Magento friendly format at this Dropbox link. Drop me a comment if that ever stops working.