IMO this will affect maybe five of the 50 states. For most Americans the mortgage interest deduction is a non-issue … IIRC this was even proposed by George W. Bush’s own tax-reform panel back in ’05.
Of course California is a different story because of rampant excess “investment” in granite countertops and multi-story backyard palapas.
And someone has to pay for the obscenely expensive bailouts, jumbo conforming / jumbo FHA loans, and other programs designed to prop up high-end real estate prices.