You’re absolutely correct. For income taxes many states and the federal government offset each others debts.

In Canada provinces can choose to harmonize taxes or collect independently.

Which misses the point. If the point is to reduce the number of taxes, having the federal government collect 10 different types of taxes instead of state governments collecting 7 types of taxes won't change all the different taxes we have.

There is no singular place we can change how many different taxes you pay. There's... thousands? Tens of thousands? Once you factor in city, county, state, federal, special districts, etc.