I don’t know if I agree with all the reasoning, because NY and CA are high income, high property value and high population states, which all contribute to their higher tax rates, but yes, I agree that it would be simple to limit property tax and state and local tax deductions to the national average. i.e. Enter the amount of your state and local taxes, but not greater than $x,xxx. Enter the amount of real estate taxes paid, but not greater than $x,xxx.
I’m aware of high population property valuation etc. But as I think about mortgage write offs. How about allowing deductions solely apply to interest rates and a given percentage of the principal ? For property tax set a fixed percentage deduction say 50% ?