New York, New Jersey and Connecticut give more per resident to Uncle Sam and receive less back than any other states. Their residents will also be hit hardest if Republican lawmakers in Congress repeal all or part of the deductions for state and local taxes.

The repeal of SALT—or state and local tax—write-offs is a centerpiece of the tax overhaul for both fiscal and ideological reasons. Eliminating the deductions that individuals get for state income, sales and property taxes could raise more than $110 billion a year.

Supporters...