Somehow it always ends up there, like that's a "legal no go". I.e. "that would have to go through the supreme court" or "that's the constitution". I realize it's hard to change some things (like how is Gerrymandering for political views allowed?) but is it that hard that it's meaningless to attempt? Doesn't that mean (in the case of the Gerrymandering example) that US democracy is fundamentally broken AND can't be repaired?
Congress could do it just by imposing a 100% tax on income attributable to an agreement providing an abatement of generally-applicable state or local taxes.