The Constitution did not create a new nation, it created a federal government to tasks that the states could not perform with assistance. In a federal government ta short list of powers were delegated to the national government, while all powers not delegated to the central government were reserved to the state.
The Constitution which was written by delegates of the states created a bicameral legislature with one house to represent the people and a second house to represent the legislatures of the states. It was to be the responsibility of the senate to prevent the House of Representatives from exceeding its Constitutional authority.
The federal government was governed by the rule of law, while a national government is governed by the will of the majority. The founders knew that the liberty of the individuals could best be preserved in a federal government.
The united States is not a nation it is a union of independent sovereign states united for the purpose of promoting their common defense and the general welfare of all of the people.