Singling out a state based on a criterion of performance is different from singling out a state by name. This goes well beyond the scope of what Rehnquist gave the nod to. Remember how ACORN managed to get their defunding overturned? This is the goose which shares sauce with that gander.
...the National Minimum Drinking Age Act, withholding 10% of Federal-Aid Highway Act funds from statesthat did not adopt a minimum legal age of 21 for the purchase and possession of alcohol.
Applied equally to all states, not SD by name.