It's often easier to evaluate compliance than it is to engineer a compliant system.

The software would have to work everywhere. The tax collections (review/enforcement, really) process only has to work in one place. Tax law in one place is usually clear enough; the complexity is in the aggregate.

My state doesn’t have to give a rip that NYC has a city surtax on this but not that, or that some other jurisdiction treats clothing items up to $100 as non-taxable while we put the limit at $175.

The federal government is only one part of it. States, counties, and cities can also impose their own income taxes or sales tax. Or like Florida they can choose not to have an income tax.

I suppose that would be like asking the EU commission to provide tax software for all its member states.

They pour the resources and money into the enforcement side instead of the collection side.