Even this writter said as much when he commented that the old Unions were "falling down around their heads". Yes the 1787 Constitutional Convention was an effort to preserve the old union, but only 5 states sent delegation at the first? That tells me that 8 states had no real interest in attending these talks of forming a New Union until the Constitution began to take on a more substancial form which guaranteed more States sovereignty. So it was that Constitution with specifically its limits on Government authority and Guarantees of rights which restored the Union of States. Now a Union of States writting a new Constitution. If that were the case then the Union would surely not have limited the powers of the central Government in the way that it was.
No government (I.E. Union) gives up it powers and authority unless it has too.