[pdog]

By this logic, with no SALT deduction cap, a state could simply implement the federal income tax brackets for its own taxes and permanently deprive the federal government of any income tax revenue by allowing it all to be deducted.

[stopping]

Not exactly. The only way a state government could deprive the federal government of federal tax income is to tax their residents at a rate of 100%. Even with an uncapped SALT deduction, the federal government is entitled to tax whatever income you have leftover after paying state/local taxes.