> So yea, it really isn't that simple in the USA.
German VAT is also not simple. Before we had a temporary (so another layer of madness) law change, you either paid 19% VAT or 7% VAT, depending on whether you ordered your food to go or sat down at a restaurant. So the same item, for the same person would be taxed at a different rate depending on whether that person walks out with the food or carries it to a table. The restaurants simply advertise a single price and eat the difference [1]. Or to be more precise: the different tax values are priced into the single price, potentially accounting for the rough split between dine-in/takeout orders.
Despite all of this madness, we see a single price at the menu, we can pay exactly that price, and for takeout it actually is not uncommon to actually pay exactly that price. No sales tax, mandatory surcharges or gratuity, just a single, final price.
As for differences in the income needs of the counties/municipalities: this is handled with taxes on the profit of companies based in that area [2]. So the consumer never sees the differences in taxes, accounting is pushed to companies. If McD wants to advertise a fixed price nationwide, their franchisees need to eat the difference.
I get that in the US the states are more like countries in the EU, but we still manage to have the same VAT in all of Germany while apparently US sales tax can vary on the city level.
[1] there are exceptions, e.g. explicit to-go foods are advertised as such
[2] there are more ways for this, but this is, IMO, the most similar way to the local sales tax in the US