[El Gato]

The Constitution is an agreement between the States.

Not entirely. The Preamble reads:

We The People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

The Constitution is a delegation of power to the national government, by the people. It's also a limitation on that power, and in some cases on the powers of the states as well. (States can't print money, or levy export taxes for example).

The states role lay in ratification. They didn't write it, but are a party to it because of ratifying it. Since they didn't make the agreement in the first place, they can hardly have made it between them.

[GrandEagle]

Since they didn't make the agreement in the first place, they can hardly have made it between them.
This is entirely incorrect.
Each state sent deligates for the specific purpose of modifying the articles of Confereraton.
What ended up happening was effectively a rewrite of government. The ratification process was the arrangement by which the State governments agreed with what their representatives developed. It is an agreement between the governments of the several States.
It is exactly an agreement between the several States.
I will conceed the point about rights vs powers. You are exactly correct.

[GrandEagle]

Since they didn't make the agreement in the first place, they can hardly have made it between them.
This is entirely incorrect.
Each state sent delegates for the specific purpose of modifying the articles of Confereraton.
What ended up happening was effectively a rewrite of government. The ratification process was the arrangement by which the State governments agreed with what their representatives developed. It is an agreement between the governments of the several States.
It is exactly an agreement between the several States.
I will concede the point about rights vs powers. You are exactly correct.