How in the world would that help the national debt?
Where do you think the feral government gets the money they "give" to the states?
They borrow it. Each year the feral government runs a deficit (even if one year's deficit is less than the previous year's deficit) adds to the debt. Every program the cities or states get a federal grant for is a program that adds to the national debt.
"Deficit reduction" is a stupid, meaningless term. Until we enact budgets that have zero deficits and include a line item for paying down the national debt, the country is teetering on fiscal disaster.