I’m saying that States cannot have Federal referendums. States can have State Referendums. More than one state can hold a referendum at the same time if their own Constitutions allow it, but they are all still State Referendums.

The Federal government does not have the power to hold country-wide referendums, it would have to be given the power through an amendment, which would also specify the parameters (and, more importantly, the limits) of this new power the people are giving to its Federal Government.

(This all assumes the Constitution still matters, which is a matter for debate these days)