It is worthwhile looking at the mechanics of the individual and collective US perspective.
Individual in high-tax-state: From an individual perspective living in a high tax state like California, not being able to deduct state taxes in excess of $10000 from federal taxes is effectively a tax increase.
For federal US as a collective: For the US as a federal whole deducting an increased state tax from federal taxes is effectively a reduction of the federal tax percentage, especially when states vote for increasing taxes to fund projects that are not delegated from democratic consensus at the federal level.
Capping the deduction at $10k per individual makes it equal for all citizens regardless of which state they live in.
This is therefore in some ways a fight between competing visions of what the US should be.
Individual in high-tax-state: From an individual perspective living in a high tax state like California, not being able to deduct state taxes in excess of $10000 from federal taxes is effectively a tax increase.
For federal US as a collective: For the US as a federal whole deducting an increased state tax from federal taxes is effectively a reduction of the federal tax percentage, especially when states vote for increasing taxes to fund projects that are not delegated from democratic consensus at the federal level.
Capping the deduction at $10k per individual makes it equal for all citizens regardless of which state they live in.
This is therefore in some ways a fight between competing visions of what the US should be.