> keeping track of exactly which taxes apply and which don't to who, from 3,143 counties and 19,495 cities isn't a trivial thing to do.

I don't see this isn't a legitimate beef. If you can't comply with local regulations because you serve too many municipalities it sounds like you aren't a good fit to serve those customers. Perhaps the solution is to sell your infrastructure off to smaller, local companies who can comply. Or heck even just other equally big companies who are well run enough to manage such a problem.