Brazil is also a federation, it is larger than continental US, and has much more complicated taxes that also vary per state and per municipality (county) -- and yet we have "European-style" laws that require that the advertised price is the full price. It has been like this since forever.

If Brazil, a much poorer country in comparison, can do it then so does the US. I think that arguments in the contrary don't hold any water and are poor rationalizations ("US is special").