I can't comment intelligently on that one Maidson letter without knowing its full context. However, one letter does not argue for unanimity of opinion on the matter during the founding period. Strong, even bitter differences of opinion existed throughout the period as regards state sovereignty vs. an all-powerful central government — or, to be more precise in describing the choice as they saw it, between preserving the newly independent states and fear of the establishment of a monarchy.
By all means, it's true that the members of the Constitutional Convention wanted to replace the weak Articles of Confederation with a stronger federal system. However, federalism meant something quite different to them than it does to us, today. Heck, it meant something different to the small vs. large states, to the northern vs. southern states, and to agrarians like Thomas Jefferson vs. urban businessmen and financiers like Alexander Hamilton. Their split on these very issues was the genesis of the American two-party system.
At one point early in the Constitutional Convention, Hamilton delivered a speech that seemed to argue for dissolution of the states entirely, and for the creation of a single central government with a monarchist slant. (Hamilton was an admirer of the British system of government.) The speech was most definitely not well-received by his fellow delegates. He left the convention and only returned months later.
In contrast, Jefferson despised the British and admired the French. He was in France at the time of the Convention. But we know from all of his writings during the period that, while he agreed with a strengthening of the federal system, he was opposed to a very strong, dominant central government. (When he finally became president, he didn't govern the way he had always written of his political beliefs, by the way.)
Over time, those who agreed with the Hamiltonian view (including Washington and Adams) became known as Federalists, and those who agreed with the Jeffersonian view became known as Democratic-Republicans. The seeds of the civil war were planted during the founding period, not just in their failure to deal with the slavery question, but also in this federalist vs. states rights question that only came to a head when South Carolina seceded.
She and the other southern states did so precisely because the states believed the Constitution did not bind them in a perpetual union. The Constitution is silent on the matter. (It would never have been ratified otherwise.) Solely as regards their right to secede, I believe the southern states were correct. Lincoln and many in the north obviously had a different view. That was the core issue of the Civil War, not slavery. Emancipation was a byproduct of Lincoln's fight to impose permanent union on the states.