>>"The States of the United States ...."
That would not be proper English nor make any sense linguistically.
If you believe that the Founders thought the States were not independent, and sovereign in their own right then you clearly have not read the Federalist Papers. Take a close look at Federalist 17 as an example
If the States were not separate but equal, i.e the foundational principle of our style of governance, then why call the nation the United *States*, why not just call it America or some other name all together
No the founders clearly believed the States should not be servant to the Federal Government, nor should the Federal Government be servant to individual state governments.
>>Second, the issue was conclusively settled at Appomattox and with the ensuing enactments of the 14th and 15th Amendments.
I disagree that it was conclusively settled, nor do I agree that application of the federal constitution to the states by default makes the states Subservient vassals of the federal government
Further last I check the passage of an Amendment requires the ratification of said amendment by 3/4 of States thus proving they are in fact not vassals as if they were then their consent would not be needed.
>In the modern era that might still be viable if the Senate's power were only to veto enactments by the House, perhaps by a supermajority vote
Yea... no
That does not make any sense historically, legislatively or logically. Having a chamber that can only act in the negative would be a pointless chamber of government.
Bills should be assumed to be Bad and at every level require affirmation.
Your process of legislative review makes about as much sense as a criminal system on the principle of Guilty until Proven innocent.
Laws should be hard to pass, laws should be extremely hard to pass, and federal laws should be almost impossible to pass ensuring the federal government does very little and most governance is done at the local level where it should be done.
In general the government that governs the least, governs the best, and this is quadruple true for a Federal Government