>The legal structure of sales taxes in the US present some unique challenges
Nothing about sales tax in the US is unique at all. It is not special. It is not hard. It is not a complex problem. It is basically a lookup, and computerized POS systems have managed it just fine since the dawn of computerized POS systems.
In fact, when those sales taxes were first implemented, there was problems relating to how to manage sales that resulted in fractions of a cent worth of sales tax to account for. Several states created sales tax tokens worth fractions of a cent and had to insist that it didn't technically count as money because states can't mint money legally.
https://en.wikipedia.org/wiki/Sales_tax_token
Nobody went to jail. It was a minor nuisance for consumers and was quickly replaced with law changes to just have explicit rules for the edge case, which is the entire reason we have legislatures. If you don't want retailers to respond to this change in a certain way, have your legislatures say that.
>This is very much a case of the Mencken quote that for every complex problem there is a solution that is simple, obvious, and wrong.
Just stop already. The US is not special. The US regularly insists it cannot do the same things everyone else does and it is just wrong. We literally have textbooks full of examples from our own country. We've already phased out coinage before.
The UK went from it's absurd money system to reasonable and decimalized money within living memory! 15 February 1971. Sweden had a day where they switched from left hand roads to right hand roads! https://en.wikipedia.org/wiki/Dagen_H Most of Europe switched to Euros in living memory as well!
Stop insisting reasonable societal problems are too hard to solve, because that's the only actual reason they are hard to solve
>These problems can't be legislated away because the authority to do so is highly decentralized.
It isn't at all. It's in the Federal government, and it's in your local state government, and it's in your local-er governments, and that is just like a lot of other countries. A couple layers isn't "very decentralized".
It is only in the past 50 or so years that a singular political party has insisted that the same political party that did all sorts of speedy and useful lawmaking for a hundred years suddenly cannot adapt quickly. Meanwhile, 48 state governments continue to function mostly fine, with few problems adapting to local specific problems in a timely manner. If your state cannot adapt to this quickly and easily and without serious issues, consider electing different people.